228 



SCIENCE 



[N. S. Vol. LIII. No. 1367 



Ttis author found that in twenty-six out of 

 thirty-one cases when the cercarise from a 

 single snail were used in infesting' experi- 

 mental animals all the individuals developed 

 ■were of the same sex. Dr. S. Tokogawa 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 rab- 

 bit was infested with the cercarise from a single 

 snail that worms of only one sex would de- 

 velop. 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 aU the cercarise coming from a single 

 miracidium are of the same sex. "When all 

 the individuals derived from the cercarise 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 

 miracidla 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 re- 

 gard to dimorphism in a species of schisto- 

 some 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 ex- 

 pected. Up to the present time, however, no 

 one has examined these stages to determine 

 whether they ^how 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 trema- 

 tode family. William W. Cort 



knowledge of the morphology and development of 

 Schistosoma japcnvicum" (Japanese). An abstra«t 

 of a paper given before the Japanese Pathological 

 Society. Igaku Chuo-ZasH, Vol. 17, No. 6. 



ORIGIN OF POTATO RUSTi 



A YEAR ago the vn-iter 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? Since then the lattei^' 

 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 sen- 

 tences from this article, after changing them 

 from the Spanish into an English garb. 



The rust of the tomato and potato is a whoUy 

 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 enor- 

 mous injuries that it occasions; these considera- 

 tions would seem to place it among the most seri- 

 ous 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 meet- 

 ing, December 29, 1920. 



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



s Boletin de Agricultura Quinta Normal, 1 : 7-12, 

 Figs. 1, 2, January, 1920. 



