448 SUMMARY OF CUERENT RESEARCHES RELATING TO 



" hood " at the posterior of the male is bilobed, with six finger-like 

 " rays " on each side, and a median forked " ray " ; in general similar 

 to the hood of S. Douglassi Cobb. There are three spicules. The 

 vulva is in the posterior sixth of the body. The body is very trans- 

 parent, allowing the viscera to be seen ; measurements are given of 

 the various organs. This Nematode is allied to that of the grouse, 

 S. pergracilis, and to the stomach-worm of lambs, S. contortus. The 

 author mentions Schneider's opinion that the larva of Simondsia 

 paradoxa exhibits a rhizocephalous condition, similar to that of 

 SaccuUna amongst the Crustacea. 



Embryonic Development of Bothriocephalidae.* — Dr. H. Schau- 

 insland has studied the embryonic development of Bothriocephalus rugo- 

 sus, B. latus, B. sp., Trisenophorus nodulosus, Ligula simpUcissima, and 

 ScMstocephalus dimorpJius ; they agree with one another in all essential 

 points. The germinal cell alone takes a direct part in forming the 

 embryo ; it exhibits a regular segmentation, and some of the cells thus 

 formed give rise to an embryonic envelope, which becomes par- 

 ticularly well developed in the non-ciliated embryos (JS. rugosus), but 

 is very delicate in the eggs that are very rich in yolk and havo 

 ciliated embryos. The embryonic cells within the yolk are generally 

 spherical and again form an epibolic covering, which does not, 

 however, extend over the whole of the yolk ; the embryo now consists 

 of a thin outer cell-layer and a compact inner mass ; the former gives 

 rise to an investment which contains a quantity of protoplasm ; this 

 later becomes vacuolated and in some forms reduced to fine proto- 

 plasmic filaments. This second investment is, or is not, ciliated ; it 

 serves as a protective or locomotor organ ; the connection between 

 the larva and its covering is always slight ; the larval body is formed 

 of two kinds of cells which differ in size, the larger being more 

 central, but the smaller peripheral cells do not form an epithelium. 

 Although the entrance of the larva of a bothriocephalid into its host 

 has never been actually observed, it is quite certain that when it does 

 so the ciliated mantle or homologous investment is cast off; all that 

 remains of the larva, and therefore of the adult worm, is of an 

 endodermal nature. This view is shown to be correct by the study of 

 development, in which gastrulation occurs as in other Metazoa ; there 

 is no cleavage cavity, but this is not remarkable, though the double 

 epiboly is. Leuckart has already expressed a belief that the adult 

 worm has no ectoderm, and this is supported by the structure of the 

 adult, in which we can distinguish no epidermis, but only cortical and 

 medullary substance. 



The author points out that the Bothriocephalidae agree essentially 

 with the Ts8niidae in the history of their development, and they still 

 more strikingly resemble the Trematoda ; their resemblances to the 

 Turbellaria and the Nemertinea have not yet been completely worked 

 out, but there is reason to suppose that so far as regards the ectoblast, 

 they will be found to exhibit really similar phenomena. If the adult 

 Cestodes have no true ectoderm, it follows that the adult Trematoda 



• Jeuaisch. Zeitachr. f. Naturwiaa., xix. (1885) pp. 523-73 (3 pla.). 



