470 REPORT ON ZOOLOGY, MDCCCXL1V. 



to tlie position of the male sexual organ ; in some Bru- 

 chylaimi for instance, the male organ opens in front of 

 the ventral acetabulum ; in others, on the contrary, it does 

 so in the middle between the ventral acetabulum and the 

 extremity of the abdomen, whilst the oviduct opens ante- 

 riorly and externally. At the extremity of the abdomen 

 of these Trematoda a pore leads into a contractile cavity, 

 from which four winding, mutually-anastomosing, lateral 

 canals proceed upwards, which are here and there furnished 

 with solitary undulating cilia. The Reporter in this 

 description recognises the excretory organ which is peculiar 

 to the Trematoda, as well as the vascular system provided 

 with ciliated lobes, which Dujardin has not distinguished 

 from that excretory organ. Besides those taken from the 

 male genital organs, Dujardin also finds in Brachylaimus 

 various other specific characters, which relate to the size of 

 the acetabula and of the ova, and to the greater or less prick- 

 liness of the cutaneous surface. The same naturalist has 

 referred to this genus a Distwnum found in Sorex araneus, 

 as Brachylaimus advena ; but has named it afterwards (in 

 his larger work on the Helminthes) Brachylaimus miyrans. 

 He derives this animal from the Distornum inhabiting the 

 Limax, which presents exactly similar acetabula, a similar 

 intestinal canal, and the same system of vessels furnished 

 with vibratile cilia, and in which the male genital apparatus 

 exhibits a form, in all respects similar ; whilst, of the female 

 sexual organs, nothing is as yet to be recognised. Similar 

 Distomata in Frogs are probably derived, in Dujardiu's 

 opinion, from Snails that have been swallowed. 



According to Kolliker's observations (Miiller's Arcliiv, 

 1843, p. 99), the ova of Distomum tereticoUe are thus 

 developed : in the midst of the compact granular viteliiiie 

 substance the primitive embryonic cells are formed, increase, 

 break through the vitellus, and entirely consume it. The 

 collective mass of the very minute embryonic cells is 

 finally transformed into the body of the embryo. -This is 

 of a vermiform shape, moves sluggishly, exhibits no trace of 



