648 SUMMARY OF CURRENT RESEARCHES RELATING TO 



JSchinorhynchus proteus and E. angustatus are very common, but 

 E. clavceceps was only found once in the rectum of Leuciscus rutilus. 



With a good deal of hesitation, a specimen found in the intestine 

 of Thymallus vulgaris is regarded as being a young form of Gordius 

 aquaticus ; such characters as were to be detected seem to justify the 

 author's view, but they are hardly sufficient for certainty. 



In an appendix a report is made on certain psorosperms which 

 were found under the skin of Coregonus /era, and appear to be the 

 cause of an affection to which this fish is subject, especially in the 

 spring ; agreeing generally with the piscine psorosperms described 

 by Balbiani, they do not exactly resemble those seen by Lunel and 

 described by Claparede ; they have two vesicles at the end opposite 

 to the " tails," whereas, in all species, according to Balbiani, they are 

 found near the tails ; as, however, these vesicles give off an extremely 

 fine canal, which passes to the base of the tail, it is probable that, as 

 in others, they serve as a sheath for these processes. 



Free-swimming Sporocyst.* — Prof. E. Eamsay-Wright records the 

 existence of a hitherto unknown form of sporocyst, one specimen of 

 which he observed recently swimming very actively in an aquarium 

 containing a few water-plants and fresh-water mollusca. In form and 

 size it recalls the larger Gercarice with forked tails, and contains a 

 single tailless Cercaria or larval Distome. In accordance with its 

 free life, the muscular system is much better developed than usual, 

 and the same is true of the water-vascular system. Of special inte- 

 rest are tactile papillae, which beset the surface, and which obviously 

 enable the sporocyst to find the definitive host for its contained larva. 



Development of Turbellaria.t — Mile. S. Pereyaslawzew communi- 

 cates a short abstract of her results obtained by studying the develop- 

 ment of the Turbellaria Acoela. The ovum divides into two equal 

 halves, from each of which a small cell is detached ; the further pro- 

 cesses of cell-division are detailed ; they result in the formation of a 

 gastrula, the smaller cells becoming the ectoderm ; the larger cells 

 form the endoderm, and also give rise to the mesoderm ; as develop- 

 ment advances the embryo takes on an angulated contour such as has 

 been figured by Metschnikoff ; when it reaches the gastrula stage it 

 becomes again rounded and clothed externally with cilia. 



Fresh-water Turbellaria of North America.| — Mr. W. A. Silliman 

 has been engaged in studying the fresh-water Turbellaria of Monroe 

 County (State of New York), and as the area is rather limited, he 

 thinks it probable that he has found all the forms that live there. 

 A comparatively large number of new species are described. 



Macrostoma sensitivum n. sp. has generative organs of much the 

 same character as those of M. hystrix, but the male orifice is not at 

 the end of the penis, but some distance behind it. The author finds 

 that forms with no schizocoel have a more richly branched water- 

 vascular system, while Microstoma and others which have a well- 



* Amer. Natural., xix. (1885) pp. 310-1. 



t Zool. Anzeig., viii. (1885) pp. 269-71. 



X Zeitschr. f. Wiss. Zool., xli. (1884) pp. 48-78 (2 pis.). 



