Endamoeba coli. Excystation of E. coli was observed many times by the writer in material obtained by washing infected feces in water. This material either in water or in weak saline solution was sealed under a cover glass and placed on the stage of a microscope confined in a warm chamber. The protoplasm within the cyst is at first finely granular and the eight nuclei are usually clearly visible, but later the nuclei become invisible and a number of larger granules of various sizes appear. The first evidence of activity preceding excystation is the movement of the cytoplasm in the center of the cyst. No large free area exists between the cyst contents and the cyst wall such as described by Smith (1927) in Iodamoeba williamsi. Pseudopodia first appear through an opening in the cyst wall. This opening is small and the protoplasm streams through it rapidly in a thin strand. The amoeba does not leave the cyst wall at once, but usually, after from one half to three fourths of the protoplasm has escaped, movement begins in the opposite direction and most or all of the animal streams back again into the cyst. This egress and return of the protoplasm may occur as often as ten times before complete escape is effected and the liberated amoeba moves away from the deserted cyst wall.

After excystation the amoeba moves at first slowly but soon flows across the field by means of rapidly forming pseudopodia. These pseudopodia are somewhat similar to those of E. histolytica, being formed rapidly and more or less explosively and being at first free from granules although not so clear and hyaline as those of E. histolytica. In every case the entire contents of the cyst emerged as a single amoeba. Excysted amoebae were watched for more than six hours, but no division stages were observed. Endolimax nana. Excystation could not be studied as easily in Endolimax nana as in Endamoeba coli because of its minute size. So far as could be observed, however, the process was similar in every respect. The first evidence of activity was movement in the cytoplasm; this was followed by a minute break in the cyst wall through which the cytoplasm protruded; then after flowing in and out several times the organism separated from the cyst wall as a single amoeba.

Chilomastix mesnili. Excystation of this flagellate was seen in only one case. The details were not clearly made out, but the essential features were observed. Movement of the protoplasm within the cyst was followed by a break in the wall at the anterior end and the rapid emergence of the organism, which soon took on approximately the shape of a typical trophozoite. One large cystostome was pres

ent. Whether the excysted specimen contained one or two nuclei was not determined. In this case the cyst was in a saline medium and excystation occurred after three hours and forty minutes at about 37° C.

Giardia lamblia. Complete excystation of Giardia lamblia in vitro has not been observed, but movement within the cyst can be brought about by the same method as that shown to be effective with other protozoa. Washed cysts from two to four days old were used. Material was sealed under a cover glass and kept in an incubator at 37° C. for two hours; it was then placed on the stage of a microscope in a warm chamber at approximately 39° C. Within from ten to fifteen minutes movement began in some of the cysts. The contents seemed to contract and expand, due probably to bending movements of the axostyle such as were observed in cysts recovered from the small intestine of the rat (Hegner, 1927). The protoplasm of the organism was seen to shrink away from the cyst wall and after from one to four hours became quiescent.

It seems safe to conclude from these observations that, as suggested above, moisture and a favorable temperature (about 37° C.) for a sufficient period (several hours) are the essential factors in excystation. It, therefore, follows that the digestive juices of the host that ingests the cysts of intestinal protozoa are unnecessary in bringing about excystation. They may be helpful, but on the other hand it is possible that they are harmful. If the latter is true, then the cyst wall probably protects the cysts from the secretions encountered in the stomach. In this connection it may be noted that no excystation nor protoplasmic movements were observed within the cysts of Giardia lamblia that were injected into the stomach of the rat, although cysts hatched in the small intestine of this animal (Hegner, 1927). Further details of excystation in these intestinal protozoa will be published in a later communication.

THE JOHNS HOPKINS SCHOOL

OF HYGIENE AND PUBLIC HEALTH

ROBERT HEGNER

ISOTOPES OF CALCIUM

THE writer has recently studied the selective reflection of several carbonates at about 6.5 microns. Polarized light was used so that bands due to vibrations along the different directions in the crystal would not be superimposed. In the case of calcite (CaCO3) three small maxima were observed. The wave lengths were 6.36 μ, 6.54 μ, and 6.62 μ. When several bands overlap, it is difficult to calculate the true intensity of the separate bands as there is no zero line of reference. However, using the band at 6.54 μ as the standard, the band at 6.36 μ is about

one twentieth as intense; also, the band at 6.62 μ is about one fifth as intense as the band at 6.54 μ. So it is likely that calcium is made up of isotopes with atomic weights of 39, 40 and 44 and of quantities in the ratio of one fifth, one, one twentieth, respectively. The atomic weights given would have the approximate separation as found for the bands. and these atomic weights with the quantities named would give a mean atomic weight about 40.

It is interesting to note that calcium has been studied for isotopes by Dempster,1 Aston2 and G. P. Thomson. Dempster found points which correspond to 40 and 44 and another set of points which correspond to atomic weight 39. However, he considered the 39 as due to potassium, which likely occurred as an impurity. Aston also studied calcium, but due to the fact that it did not produce anode rays easily, he did not find a line for calcium of atomic weight 44. Aston carefully excluded potassium from the mixture, but the line corresponding to atomic weight 39 was more intense than the 40 line. So the line at 39 was possibly a mixture of potassium and calcium. G. P. Thomson's work on calcium gives a broad line at 40 which was not resolved by his instrument. However, he states that there must be another line at 39 or 41 making calcium an isobar with potassium. So it is likely that calcium has an isotope of atomic weight 39. In addition to the above facts it appears that it would have been very difficult to detect the isotope of atomic weight 44 if the intensity were only one seventieth of that of atomic weight 40. It could not have been observed by the method of band spectra used by the writer. It seems probable, therefore, that the isotope Ca is present to a greater extent than one seventieth and that a mean atomic weight of 40.07 is made possible by the presence of Ca39.

UNIVERSITY OF NORTH CAROLINA

E. K. PLYLER

A PRE-CHATTANOOGA SINK HOLE1 THE Chattanooga shale is locally five to seven times the thickness generally observed in the region of the Gainesboro, Tennessee, quadrangle. This fifteen-minute quadrangle, ten miles south of the TennesseeKentucky line, was mapped by the Topographical Branch of the United States Geological Survey in 1925. Through it the Cumberland River swings in entrenched meanders four hundred feet below the

1 Physical Rev., 18, 421, 1921.

2 Aston, "Isotopes," p. 101. 3 Phil. Mag., 42, 857, 1921.

1 Printed with the permission of the state geologist of

Tennessee.

level of the dissected Highland Rim Plateau.2 The Fort Payne formation of lower Mississippian age is at the surface of the plateau throughout the area. Beneath the Fort Payne a green shale, varying in thickness from a few inches to one or two score feet, lies upon the Chattanooga shale. The Leipers, Catheys and Cannon strata of Ordovician age, together four hundred feet thick, are separated from the Chattanooga shale by a disconformity. The rocks of the region are gently arched in a northeastern extension of the Nashville Dome.

The writer spent three and a half months of the 1926 field season mapping the areal geology and structure of the Gainesboro quadrangle for the State Geological Survey of Tennessee. An interesting result of the summer's work was the discovery of an extraordinary local thickness of the Chattanooga shale. This body of shale is generally ten to fifty feet thick in the Nashville Basin and adjacent areas. According to general observation, the thickness does not vary more than five or ten feet in many miles.3 The writer found the thickness to exceed 149 feet on Flynn Creek, five miles south of Gainesboro. The shale is exposed in several places in the vicinity with seventy-five or ninety feet of strata visible in a continuous outcrop. It lies in an irregular closed depression or series of depressions in a limestone conglomerate-breccia which is at the same altitude as Leipers, Catheys and Cannon strata. The actual contact of the breccia with formations other than the shale was not seen. Some of the blocks in the breccia contain fossils common to the Leipers and Catheys, but the fossils do not determine with certainty the formations from which the blocks were derived. Some of the blocks differ in lithology from the preChattanooga strata heretofore observed in this general area. It is possible that a detailed and thorough study of all the blocks might yield information which would partially close the hiatus between the Leipers and Chattanooga deposits. The breccia is more than one hundred feet thick in some places.

2 Purdue, A. H., "General Oil and Gas Conditions of the Highland Rim Area in Tennessee," Resources of Tenn., Vol. 7, No. 4, pp. 220-228. 1917.

3 Butts, Chas., "Geology and Oil Possibilities of the Northern Part of Overton County, Tennessee, and of Adjoining Parts of Clay, Pickett and Fentress Counties," Tenn. State Geol. Survey Bull., 24, pt. 2-A. 1919. Hayes, C. Willard, and Ulrich, O., U. S. Geol. Survey Geol. Atlas, Columbia folio (No. 95). 1903. Mather, Kirtley F., "Oil and Gas Resources of the Northeastern Part of Sumner County, Tennessee,'' Tenn. State Geol. Surv. Bull. 24, pt. 2-B. 1920. Miser, Hugh D., "Mineral Resources of the Waynesboro Quadrangle, Tennessee," Tenn. State Geol. Survey Bull. 26. 1921.

The extent of the increased thickness of the Chattanooga shale and the presence of the conglomerate breccia coincide in an irregular area about two miles in diameter with outcrops visible in the valley of Flynn Creek and its tributaries, Rush Fork, Cub Hollow, Lacey Hollow and Steam Mill Hollow, where they join that stream. Outside this area the Chattanooga shale is about twenty feet thick and rests disconformably upon the Leipers limestone. Gentle dips obtain throughout all but this part of the Gainesboro quadrangle. Here the Ordovician limestone strata dip at 15°, 20°, and even higher angles. On the south, east and north the dips for short distances are toward the area. On the west there may be surficial faulting of the Ordovician. The top of the shale is at a lower altitude where it rests upon the brecciated limestone than at adjacent outcrops, in general being lowest where the shale is thickest. This difference in the altitude of the top of the shale amounts to more than one hundred feet as determined by stadia and telescopic alidade. Where the shale is nearest its normal altitude, it is thin and lies upon hills of the conglomerate-breccia.

Several hypotheses were considered at the time the writer was investigating and mapping this peculiar feature. The figure obtained for the thickness was questioned, for in landslides strata that are high on the sides of a valley may slump to the bottom of the valley with their attitude practically unchanged. But the shale is completely exposed in sections up to ninety feet thick in single outcrops, and it crops out practically continuously in the bed of Flynn Creek and tributaries with the same system of joints throughout.

The question arose as to the possibility of postChattanooga diastrophism restricted to this small

area.

There might have been subsidence, or perhaps uplift followed by subsidence which deformed the shale so that at this one place it is exposed in the bed of Flynn Creek, whereas, both upstream and downstream from this locality, its base is high on the sides of the valley. The diastrophism might have proceeded in such a way as to produce the brecciation and high dips in the limestone. Bucher has described a circular area of intense folding and faulting in Adams County, Ohio, and refers it to the class of "crypto-volcanic" structures. However, the thickness of the shale and the absence of folding or brecciation of the shale and overlying beds, which are structurally conformable, indicate that the Chattanooga shale and later formations could not have been affected by such diastrophism. Moreover, the 4 Bucher, Walter H., "Crypto-volcanic Structure in Ohio of the Type of the Steinheim Basin" (abstract): Geol. Soc. Amer. Bull., Vol. 32, no. 1, pp. 74-75. 1921.

actual exposure of the contact of the shale and breccia shows an irregular erosion surface which is not paralleled by the contact of the Chattanooga shale with the overlying green shale at the base of the Fort Payne chert. The conglomeratic nature of the breccia and the absence of veins or dikes of possible igneous origin discourage the view that sub-surface vulcanism may have been the cause of the diastrophism, either before or after Chattanooga time.

From the observed facts noted above, it is clear that at the inception of the deposition of the Chattanooga shale there must have been a depression with an irregular outline and an uneven floor. In the bottom of the depression and along the walls there were considerable thicknesses of slightly rounded fragments of limestone derived in part from the Ordovician limestones still represented in the surrounding area. Possibly there were also fragments from still higher strata, now eroded and entirely removed except at this one place where they are thus represented. A depression of this sort could be formed by the collapse of the roof of an irregular branching cavern or series of caverns. The fragmentation induced by collapse, together with the slope wash of talus towards the lines of collapse, would form the conglomerate-breccia.

The Chattanooga shale was deposited in this depression when the general area was receiving carbonaceous mud in the latest Devonian or earliest Mississippian time. With the loading of the region by later sediments, the mud was compacted by the squeezing out of its fluids. The fissility was produced by the orientation of mineral flakes during this process of dehydration. The fissibility is observed to be parallel to the bedding except where it conforms to ancient hillslopes. Here true bedding was not found, but since the fissility is inclined as much as 30°, it is to be doubted if the newly deposited layers stood at that high angle. The average altitude of the top of the shale is generally less in this area because in so thick a body of shale the total amount of compacting was proportionately greater, although part of the difference in elevation may be accounted for by the gentle folding of the region.

It is doubtful if this is the only feature of the sort; others exist but have remained unnoted. The existence of a sinkhole with a depth of nearly two hundred feet indicates that in pre-Chattanooga time the altitude of this part of the continent was probably at least two hundred feet above sea-level long enough for sinkholes to be formed of the general size of many of the present depressions in the area of the Standingstone quadrangle, Tennessee.

HARVARD UNIVERSITY

RALPH G. LUSK

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ANIMAL LIFE IN HOT SPRINGS

THOUGH always in hot water, many forms of animal life that inhabit the geysers and thermal springs of Yellowstone National Park and similar regions the world over appear to thrive and enjoy life, according to an article by Professor Charles T. Brues, of the Bussey Institution, which will appear in the forthcoming number of the Quarterly Review of Biology.

Professor Brues has conducted investigations in Yellowstone Park, and assembled data from studies in other parts of the world, all of which indicate that practically all of the principal fresh-water forms of life, and many that inhabit brackish or briny waters as well, are represented in the populations of these steaming baths. None of the animals favors the hottest waters, which reach temperatures between 190 and 200 degrees Fahrenheit, though plants of lowly classification can live in these places. The animals live in the cooler parts of the springs, though even in these the water is continually as hot as the hottest summer day at noon. Thus, he found water-beetles in water of 90 to 100 degrees, the larvae of a species of horsefly at 91 degrees, a water-bug at 96 degrees, snails at the same temperature, and bloodworms at 120 to 124 degrees. He found a small animal related to the crayfish in slightly cooler but still tepid water, and identified it as the same species that lives in the Arctic in ice-cold ponds.

Temperature, Professor Brues states, is not the only problem these animals have to solve. When the water is warm it holds but little oxygen in solution, and they have to breathe somehow. Some of them, like the mosquito "wrigglers," do so by coming to the surface for air, while others seem to have adapted themselves to the small supplies of this necessary element afforded by the water. Moreover, the water frequently contains an excess of carbon dioxide in solution, and sometimes poisonous chemicals, such as sulphuretted hydrogen gas and arsenic, and they have to be able to withstand these. Finally, the water always has either limestone or silica in solution, and the former is especially ready to precipitate if the temperature drops a little, threatening constantly to enclose in a mummy-case of chalky material any small animal luckless enough to be caught away from water hot enough to keep the stony material properly dissolved.

RESULTS OF INBREEDING ON NORFOLK ISLAND

PROVIDING the original stock is sound, inbreeding among human beings results in no deterioration, physical or mental. Nor does mixture of widely differing races produce an inferior type. Such are the conclusions of Dr. Harry L. Shapiro, ethnologist of the American Museum of Natural History, from recent study of the inhabitants of Norfolk Island, a small island north of New Zealand. They are Tahitian-English half-castes whose history dates back to the mutiny of the crew of the ship Bounty in

1789. At present there are more than 600 of these islanders and they are the descendants of twelve Tahitian women and nine Englishmen, part of the mutinous crew. In 1789 the crew of the Bounty, a vessel sailing in the southern Pacific, mutinied, casting the captain adrift in a small boat and making for Tahiti. Here nine of the crew, fearing capture, sailed to Pitcairn, a small uninhabited island east of Tahiti. They took with them twelve Tahitian women and nine Tahitian men. On Pitcairn the women were divided among the Englishmen as wives. The Tahitian men were allowed no women. This led to jealousy and the Tahitian men were killed, leaving no descendants. The Tahitian women and the Englishmen all of them sound stock established a line of half-castes. They were completely isolated and they multiplied rapidly.

By 1856 the population was too great for the small space of Pitcairn. More than 150 moved to Norfolk Island which was at that time uninhabited. To-day there is a population of 600 on Norfolk Island and 175 on Pitcairn, all the descendants of the original Tahitians and English. It is of the Norfolk Islanders that Dr. Shapiro has made a study.

Dr. Shapiro has found these islanders to be of sound physique, taller than the average English and Tahitians, and of good mentality. There is only one feeble-minded person, he said, on Norfolk Island. Their education has of necessity been rudimentary for generations, but they are now provided with teachers by the Australian Government under the jurisdiction of which they come. And the teachers are getting excellent results.

Thus, according to Dr. Shapiro, the Norfolk Islanders prove that, when the stock is sound to begin with, intensive in-breeding makes for no decrease in stamina. Likewise, race mixture, in his opinion, brings no deterioration.

The idea that the half-caste is inferior, he maintained, comes largely from the fact that pure races have always looked down on the half-caste. In Norfolk Island, he said, the half-caste has a chance to show his worth, for there is no discrimination against him, as the entire population is half-caste. And Norfolk Island, he pointed out, is one of the only places in the world in which no stigma is attached to half-castes.

THE COMING ECLIPSE OF THE MOON AMATEUR astronomers will have the opportunity of aiding their professional brethren in observing the eclipse of the moon on the early morning of June 15. The eclipse will be visible throughout the country, clear weather permitting, and Dr. Willard J. Fisher, of the Harvard College Observatory, has made a special appeal for amateur observations. Persons living in the southwestern part of the United States will probably have the best chances.

"Clouds are possible at even the biggest observatories," he said, "and the results of a few amateurs may be valuable on that account, if for no other reason.