Respiration in Invertebrate Animals. 337 



he defines the alimentary system of Tania and Bothriocephalus. 

 The blood system described by M. Blanchard in these worms ^oes 

 not exist. "That which he so beautifully pictures as the gastric 

 apparatus, consisting of straight capacious lateral canals, joined 

 by cross conduits, constitutes really an order of passages tun- 

 nelled in the solid parenchyma of the body, answering m every 

 sense to a normal chylaqueous system. The contamed liquid is 

 not blood, but chylaqueous fluid* : it is a flmd which is devoid 

 of eveiy trace of morphotic elements. Why it is so will be im- 

 mediately understood. , ^ ht -oi i. j 

 In the Trematoid worms the blood-vessels of M. Blanchard 

 fall unquestionably under the denomination of a chylaqueous 

 system. In Distomum hepaticum it is perfectly easy to reduce 

 to demonstration its entire characters. A large median, irre- 

 arilar channel commences in smaller passages near the posterior 

 or generative sucker, and proceeds as far as the caudal end ot 

 the body of the worm, exhibiting a gradually dimmishmg dia- 

 meter. Viewing the object transparently, it may be proved first 

 that this channel is a hollow space by the rolhng to and fro ot a 

 contained fluid; the movements of the fluid being rendered ap- 

 parent to the eye by the presence of minute accidental molecules. 

 In other respects, it is a perfectly homogeneous non-corpuscu- 

 lated fluid. By Bojanus, Mehlis, Nordmann, and other ob- 

 servers this channel is defined as terminating m an orifice pos- 

 teriorly, and the channel itself, from the limpid character of its 

 fluid contents, is described as the great duct of an excretory 

 system. This is an error. This system in the Trematoid En- 

 tozoa has neither an inlet nor an outlet. It is a closed system, but 

 not therefore a blood-system. In Distomum there is only one 

 central space: it is not a blood- trunk; it represents unques- 

 tionably the visceral cavity. These worms are not literally 

 therefore sterelminthous, sohd, or parenchymatous worms 

 (Vers intestinaux parenchymateux , Cuvier). The cavity is dis- 

 tributed in form of irregular, imparietal, reticulate passages. 

 These passages can be traced with facihty throughout the whole 

 substance of the body. They ramify profusely underneath the 

 skin and amid the digestive diverticula. They arise in the 

 most unequal manner from every point of the circumference of 

 the central trunk. They end peripherally in numerous ^stances 

 in ccecal terminations, corresponding with the mode m which the 



* The author is here desirous to explain that he does not deny altogether 

 the existence of a blood-proper system in the Cestoid worms. His re- 

 seLches enable him only to affirm with confidence that those channels 

 which are described by M. Blanchard as constitutmg an independent system 

 of blood-vessels do not exist; that his ahmentary is really a chylaqueous 

 system, and that his ovarium is truly a grand digestive organ. 



