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GENERAL OUTLOOK

As the result of a more general recognition of the basic importance of mineralogy in pure and applied science and in various branches of industry, and with a national society boasting of a membership including the progressive investigators and devotees of the subject, and with a well established and widely recognized official monthly publication, the future of mineralogy in America is assured. The problems of really fundamental significance requiring a comprehensive knowledge of crystallography and mineralogy are indeed many. The applications of the methods and truths of our science are constantly increasing and if America is to assume leadership in this great field it can be most speedily and advantageously accomplished through the friendly cooperation of the members of an organization such as this.

EDWARD H. KRAUS

MINERALOGICAL LABORATORY, UNIVERSITY OF MICHIGAN

SEX IN THE TREMATODE FAMILY SCHISTOSOMIDÆ1

THE trematode family Schistosomidæ in addition to containing three species which produce important human diseases, viz., Schistosoma hæmatobium, S. mansoni, and S. japonicum, is interesting because it is the only group of the trematodes in which the sexes are separate in the adult stage, which lives in the vertebrate. In this stage there is an extreme sexual dimorphism, the structure of the male being adapted for grasping the female in the gynæcophoric canal during copulation and the female having a very long slender body. The complete life cycles of the three human species of this family have been worked out in the last seven years, making it now possible to attack the problems related to the determination of sex and the development of sexual dimorphism.

Just what is involved in these problems can

1 From the department of medical zoology of the school of hygiene and public health of the Johns Hopkins University.

perhaps be made clear by a brief outline of the life cycle of one of the human species of this family, Schistosoma japonicum. The adult of this species lives in the bloodvessels of the liver and mesenteries of man and other mammals in the far East. The adults are almost always found in copulation in the vessels of the hepatic portal system. The fertilized ovum develops into the miracidium within the egg shell before the egg escapes

from the host. The miracidium hatches almost immediately when the egg is voided into the water and dies within a short time unless it comes in contact with a small species of snail, Blanfordia nosophora (Robson). It penetrates vigorously into this snail and metamorphoses into a sac-like structure known as the mother sporocyst. The germ cells of the miracidium are carried over directly into the mother sporocyst and develop by parthenogenesis into daughter sporocysts. A single mother sporocyst may live for a considerable period of time and produce several hundred daughter sporocysts. These daughter sporocysts also carry germ cells and produce by parthenogenesis cercaria which are the larvæ of the diœcious vertebrate-dwelling adults. These cercariæ escape into the water and will penetrate directly through the skin of any suitable host with which they come in contact. From the skin they make their way to the blood vessels of the liver, where they develop to sexual maturity in about three to four weeks. In fact I have seen copulation in an experimentally infested mouse nineteen days after exposure to these cercaria.

The first question which naturally arises in connection with the sex phenomena in this life cycle is how far back can the sexual dimorphism be traced in the development of the adult from the cercaria in the final host. In a recent series of studies on the development of Schistosoma japonicum in experimentally infested mice I have been able to distinguish males from females in specimens about 0.3 mm. in length. Since the body of the cercaria of this species is about 0.15 mm. to 0.20 mm. in length and the smallest sexually mature forms have a length of about

4 mm. to 5 mm. it can be seen that the sexual dimorphism can be noted at a very early stage. Even in the smaller stages the males have a distinctly larger oral sucker than the females and the body is wider. Also early in development the females show a larger space between the intestinal ceca in front of their point of union than do the males. As development proceeds the differences in size between the suckers of the sexes becomes more distinct. The males become broad and flat and finally the sides of the post-acetabular region curl up to form the gynæcophoric canal. In the females the body tends to become round in cross section and the width is constantly much less than that of males of the same age. A detailed description of this development will be made in a future publication. Fujinami and Nakamura2 in a paper published in Japanese antedate my findings on early sex dimorphism in Schistosoma japonicum. They were able to distinguish the sexes in specimens 0.5 mm. to 0.7 mm. in length, which developed in dogs. They laid especial emphasis on differences in the width of the body and in the character of the intestinal ceca as characters for distinguishing sex.

The next question which arises in this connection is whether sexual dimorphism is present in schistosome cercaria. Although many workers have made studies and measurements of the cercariæ of the human schistosomes no one has reported such differences. I have myself examined a number of cercariæ of S. japonicum with this point especially in mind without noting any dimorphism. Dr. S. Yokogawa, of the Medical College of Formosa, also informs me that he has made an extensive series of examinations and measurements of this cercaria in an attempt to find sexual differences without success. Since the cercaria of the human schistosomes are very small and can extend and contract their bodies to an unusual extent, slight size differences might escape notice in the living

2 Fujinami, A., and Nakamura, H., 1911, "A demonstration of some specimens showing the development of Schistosoma japonicum" (Japanese). Bio ri Gaku Kaishi, Vol. 1.

specimens and be difficult if not impossible to detect in measurements of preserved material.

Recently in some studies on a species of schistosome cercaria with eyespots from Planorbis trivolvis from Douglas Lake, Michigan, I have been able to demonstrate two distinct size types. This difference in size came to my attention first when I found that the curve plotted from the measurements of cercariæ from a number of infected snails was distinctly bimodal. More extensive studies showed that the cercaria of this species fell into two distinct size groups. I further found from measurements of the cercariæ from eleven infested snails that in the cercariæ coming from a single snail only one of the size types was represented. The difference in size was so great between these two types that it could be recognized with the naked eye when free-swimming cercariæ of the two types were placed in separate bottles. Measurements of the length of the body of the larger type showed a range of variation from 0.234 mm. to 0.28 mm. while in the smaller type the range was from 0.207 mm. to 0.24 mm. Other measurements of the body and tail, which in this species is unusually large, showed like differences. The adult into which this cercaria develops is not known, although unsuccessful attempts were made to introduce it into ducks and rats. An analysis of its structure, however, places it near to the human schistosomes in the family Schistosomida. This relationship means that in all probability in the adult stage of this species the sexes are separate. I therefore interpret the size differences in this species of cercaria as a sexual dimorphism. If this view is accepted the fact that in one infested snail only one of the types of cercaria is represented immediately becomes very significant. A more detailed account of the dimorphism of this species of cercaria will be published later in connection with a study of its structure and activities.

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This author found that in twenty-six out of thirty-one cases when the cercariae from a single snail were used in infesting experimental animals all the individuals developed were of the same sex. Dr. S. Yokogawa has given me permission to use in this connection the results of some of his experiments along this line, which were performed several years ago. He found that when a cat, dog, or rabbit was infested with the cercariæ from a single snail that worms of only one sex would develop. He also found that in these cases the worms would not develop to maturity. These two workers have developed independently the same hypothesis to explain the results of these experiments.

According to this hypothesis sex in the schistosomes is determined in the fertilized egg and all the cercariæ coming from a single miracidium are of the same sex. When all the individuals derived from the cercariæ from a single snail were of the same sex it would follow that the infestation in this snail was from a single miracidium or two or more miracidia of the same sex. In those cases where both sexes came from the same snail, this snail must have been originally infested with two or more miracidia representing both sexes. Now my findings recorded above in regard to dimorphism in a species of schistosome cercaria, and the presence in one snail of only one of these types, lends further support to this hypothesis. Further, since in the life cycle of S. japonicum, the miracidium and the mother sporocyst are the only stages derived from a fertilized egg, it is in these stages that sex differentiation would theoretically be expected. Up to the present time, however, no one has examined these stages to determine whether they show a sexual dimorphism. My purpose in discussing the data given above and the hypothesis derived from them in this preliminary way is to call the attention of zoologists interested in the problems of sex to the interesting condition found in this trematode family. WILLIAM W. CORT

knowledge of the morphology and development of Schistosoma japonicum” (Japanese). An abstract of a paper given before the Japanese Pathological Society. Igaku Chuo-Zashi, Vol. 17, No. 6.

ORIGIN OF POTATO RUST1

A YEAR ago the writer called attention to the threatened introduction into the United States of two more crop pests, the potato rust, Puccinia Pittieriana, and the peanut rust, Puccinia Arachidis.2 Since then the latter fungus has been found in one field in Florida, where all vestige of it was at once destroyed. The other fungus has not yet appeared in the United States.

During 1918 the potato rust was very abundant and harmful in the experiment station grounds at Ambato, Ecuador, not only upon potatoes but even more so on tomatoes. This was the first report of the rust in South America, having previously been known only from the high lands of Costa Rica on the potato alone. In Ecuador it showed decided preference for North American varieties of the tomato. An excellent illustrated account of the rust and its behavior, with conjectures on its origin, was published in the bulletin of the Ambato station for January, 1920, by the station botanist, Abelardo Pachano. I take the liberty to quote a few disconnected sentences from this article, after changing them from the Spanish into an English garb.

The rust of the tomato and potato is a wholly new disease, not only in our fields [in Ecuador], but also elsewhere. Not simply the fact of its nov. elty should interest us, but more particularly its virulence, its ease of propagation, and the enormous injuries that it occasions; these considerations would seem to place it among the most serious maladies of cultivated crops.

The history of this rust [in this region] may be easily sketched. The year 1918 is demonstrated as the date of its first appearance. In fact in the spring of that year we had occasion to observe very grave disturbances, by our horticulturists given the general name of plague, in the tomato plots from seed of North American origin. The varieties most attacked were those by the names Acme, Golden Queen and Black-eyed State. Nearly at the same time we noted similar lesions

1 Presented to the Mycological Section of the Botanical Society of America at the Chicago meeting, December 29, 1920.

2 SCIENCE, 51: 246-247, March 5, 1920.

8 Boletin de Agricultura Quinta Normal, 1: 7-12, Figs. 1, 2, January, 1920.

in the parcels of potatoes of the variety Calvache. But although the malady has increased very rapidly and is abundant in the tomato plots, it has not flourished in those of the potato.

.

Where did this new parasite come from? We have not met with it up to the present on any of our wild Solanaceæ, so as to enable us to infer that it has been transferred from them to the potato and tomato; neither has seed been received from Costa Rica so we could believe that it has come from that locality. The trouble, as it has manifested itself, has appeared on plots grown from North American seed, in a way to make us think that this new plague is to be referred to the United States.

Mr. Pachano informs me by letter that the disease was not so prominent during 1919 as it was in 1918, but had the same relative predominance on the tomato, especially on the North American varieties. He has also modified his views regarding its origin. We may assume, I think, that the susceptibility of North American varieties has no special significance in connection with the question of the native host or habitat. The snapdragon rust has been known since 1897, and has spread throughout the United States, but only recently has it been traced to its native Californian hosts. In fact I think we can safely assume that the appearance of the potato rust in the gardens of central Ecuador indicates that the rust can be found on uncultivated native plants in that same region. The Solanum rusts of tropical and semi-tropical America are numerous, but have been little studied, and those of Ecuador almost not at all.

There is a rust described from Colombia on Sarache edulis, a close relative of Solanum, which much resembles the potato rust except that it has slightly larger spores. This same rust on another species of Sarache was found in the vicinity of potato rust on Mt. Irazú in Costa Rica by E. W. D. Holway, who tells me that the plant is common in gardens there, going by the name "yerba mora." There is also a very similar rust known on the wild Solanum triquetrum, a vine ranging southward from central Texas into the adjacent region of Mexico, but this form has slightly

smaller spores than the potato rust. Only actual trial can show if these forms can be transferred from one host to another, and if the size of the spores is in anywise dependent upon the host.

A variation in spore-size apparently dependent on the host is found to occur in the case of the snapdragon rust, and cases of such size variation are known for other species, some of them authenticated by pedigree cultures. The spores from the potato and tomato are remarkably uniform in size. Whether the three forms of Solanaceous rusts here referred to are the same or not, it is fairly safe to predict that the potato rust has originated somewhere between Ecuador and Costa Rica on hosts native to the localities.

PURDUE UNIVERSITY, LAFAYETTE, INDIANA

J. C. ARTHUR

SCIENTIFIC EVENTS

A WORLD ATLAS OF COMMERCIAL GEOLOGY WITH the growth of American industries the known and the possible sources of our supplies of raw materials have become of greater and more pressing interest. Even the United States-most favored of nations in abundance and variety of raw materials-can not be self-sufficient; it must look beyond its shores for supplies as well as for markets. The study of the distribution of mineral raw materials and their relations to the promotion of trade and the control of industry is a branch of geology and may best be termed commercial geology. Under the complex requirements of present-day life no continent, not even North America, can be self-sustaining. It is no longer enough for us to make an inventory of the mineral wealth of the United States; we must supplement that inventory by a broad understanding of world demand and supply. To set forth graphically and to describe concisely the basic facts concerning both the present and the future sources of the useful minerals is the purpose of a World Atlas of Commercial Geology just

issued by the United States Geological Survey, Department of the Interior.

The output of the essential minerals in 1913, the latest normal year, may at least be regarded as a measure of the "quick assets " possessed by each nation, and the first part of the World Atlas of Commercial Geology has therefore been planned to show the distribution of mineral production in 1913.

The practical value of this exhibit of the world's mineral assets is evident. Experience gained during the World War emphasizes the advantage of an adequate supply of raw materials close at hand, yet that there are certain economic limits to domestic independence in raw materials is clearly shown by the readjustments already made. The more facts we possess bearing upon the relative quantity and the relative availability of the mineral resources of our own and of other countries, the better able will be our captains of industry to decide whence they should derive their raw material. The mines of the United States should be looked upon primarily as tributary to the many mills, shops, and factories in which the skilled labor of the country may find its opportunity for a livelihood. The output of raw minerals measures only the first step in industry.

More than a score of geologists have cooperated in the preparation of this atlas, which was first undertaken during the World War as a part of the task of keeping American industries supplied with raw material and is to be regarded therefore as a byproduct of the war-time activities of the Geological Survey.

AWARDS OF THE LOUTREUIL FOUNDATION OF THE PARIS ACADEMY

AMONG the awards made this year, as we learn from the report in Nature, are the following:

(1) 10,000 francs to Charles Alluaud and to R. Jeannel, for the study of the zoological and botanical material collected by them in the high mountains of eastern Africa and for the publication of the results.

(2) 5,000 francs to Jules Baillaud, for the es

tablishment of a recording microphotometer of the type suggested in 1912 by P. Koch.

(3) 3,000 francs to Henry Bourget, director of the Marseilles Observatory, for the Journal des Observateurs.

(4) 2,000 francs to Clément Codron, for his researches on the sawing of metals.

(5) 5,000 francs to the School of Anthropology, for the publication of the Revue d'Anthropologie. (6) 4,000 francs to Justin Jolly, for the publication of a work on blood and hæmatoporesis.

(7) 7,000 francs to Louis Joubin, for the publication of the results of the French Antarctic Expedition.

(8) 3,000 francs to the late Jules Laurent, for the publication (under the direction of Gaston Bonnier) of a work on the flora and geography of the neighborhood of Rheims.

(9) 3,000 francs to Henri Brocard and Léon Lemoyne, for the publication of the second and third volumes of their work entitled "Courbes géométriques remarquables planes et gauches. ''

(10) 2,000 francs to A. Menegaux, for the Revue française d'Ornithologie.

(11) 5,000 francs to Charles Nordmann, for his researches on stellar photometry.

(12) 8,000 francs to the Zi-Ka-Wei Observatory, in China (director, R. P. Gauthier), for recording time-signals from distant centers.

(13) 2,000 francs to O. Parent, for his studies on a group of Diptera.

(14) 10,000 francs to G. Pruvot and G. Racovitza, directors of the Archives de Zoologie expérimentale et générale, for this publication.

(15) 6,000 francs to Alcide Railliet, for the publication of researches on the parasites of the domestic animals of Indo-China.

(16) 4,000 francs to J. J. Rey, for the publication of a botanical geography of the Central Pyrenees.

(17) 10,000 francs to Maximilien Ringelmann, for researches relating to the physical and mechanical constants of metals intended to be used in the construction of agricultural machines.

(18) 12,000 francs to the Academy of Sciences, for the establishment of a catalogue of scientific and technical periodicals in the libraries of Paris.

It was pointed out by the council in 1917, that, although the special object of this foundation was the promotion of original research, up to that time requests for assisting work to be carried out according to a well-defined scheme had been exceedingly few in number.

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