384 SUMMARY OP CURRENT RESEAROHES RELATING TO 



there is a CEecal glandular tube, which appears to be a degenerating 

 ootype, which now probably serves as the organ which secretes the 

 fluid which, on hardening, forms the chitinous shell of the egg. In 

 addition to what the author has already discovered in the characters 

 of the excretory system, he is now able to state that the large trunks 

 are formed of flattened clear cells, that the lacunae are filled with 

 corpuscles, and that there are very delicate canaliculi, without any 

 proper wall, which unite the lacunsB with one another. In opposition 

 to Lang, the author still regards these lacunsB as representing a true 

 coelom. Hgemoglobin has been detected in the anterior part of the 

 body. 



Opisthotrema, a New Trematode.* — P. M. Fischer describes a new 

 Trematode, which he calls Opisthotrema cochleare, and which was taken 

 from the tympanic cavity of Halicore dugong ; it is remarkable for the 

 characters of its generative organs, and especially for the fact that 

 they open at the hinder end of the body — hence the generic name. 

 These openings are separate from one another, ventral in position, and 

 placed at the base of a circular pit with well-defined margins. 



The testes are paired and symmetrical, rounded in form, but more 

 or less distinctly lobed at their periphery ; as the production of sper- 

 matozoa increases, the lower segment of the testes approaches nearer 

 and nearer to the ventral surface. The testes consist of tubes, often 

 closely packed, and bounded by a homogeneous structureless envelope, 

 which is, apparently, a direct continuation of the cuticle. The 

 separate tubes are connected together by a fibrous connective tissue, 

 and are covered by a common envelope which appears to be of the 

 same structure as that of the separate tubes. In young examples, 

 naked, epithelial, finely granulated cells are to be found within the 

 tubes ; these, by division, give rise to the cells which, in older forms, 

 are found grouped into rosettes : with these are associated thick cords 

 of compressed mature seminal filaments. 



Like the testes, the seminal ducts are paired, and have the common 

 testicular investment continued on to them, while the extremely 

 delicate muscular layer is now better developed. As the ducts enter 

 the penial sheath they become united, and their lumen widens out, 

 being here homologous to the so-called vesicula seminalis anterior of 

 other Trematodes ; the width of the coiled tubes varies with the 

 maturity of their contents. The penis is so arranged that, on its 

 extension, there is a pressure on its cavity and on the full seminal 

 reservoir, the contents of which are thereby forced into the vagina. 

 The penis has no armature of spines. 



As in other Trematodes, the unpaired ovary is followed by the 

 yolk-glands and the complex of shell-glands ; connected with the 

 oviduct is a receptaculum seminis, which is of very regular ellipsoidal 

 form in young, though not in old individuals. 



In discussing the mode of fertilization of the Trematoda, the 

 author points out that there may either be self-impregnation or 

 conjugation with another individual. The former may be effected by 



* Zeitschr. f. Wiss. Zool., xl. (1884) pp. 1-41 (1 pi.)- 



