ON ENTOZOA. 551 
appears by no means probable, it is contained in the parietes 
themselves of the intestines. 
The termination of the intestinal canal, or anus, is always 
medial, and yet approaching to be terminal. 
This is the first sort of digestive apparatus found in the 
entozoa. In the second sort, there is still a terminal mouth, 
in the form of a sucker, and without armature ; but the intes- 
tinal canal, which originates from it, after having been pro- 
longed towards the middle of the body, is lost immediately 
in vasculariform ramifications, which proceed into all its 
parenchyma, and then there is no trace of anus. 
Finally, in the third sort, the digestive system does not 
commence by a single medial orifice, or by a true mouth. 
There is even no true intestinal canal, but two or more an- 
terior and lateral pores or orifices spring from the vessels 
which are united to two lateral trunks; these are prolonged 
throughout the entire length of the body, anastomosing 
together, and ramifying, without doubt, into the parenchyma 
of the animal. This is the organization of the teniz, &c. 
Tn the ligula, which are the most simple of all binary ani- 
mals, we can no longer recognize any trace of an intestine, 
of whatever sort it may be, and consequently no circulatory 
system. . , 
A special respiratory apparatus exists in none of the ani- 
mals of this class. The organ, therefore, of respiration is 
essentially limited to the skin, nor is there, in fact, any true 
respiration, except in certain families, where something like 
circulation may exist. 
The blood, or recrementitial fluid, has been but little 
studied. 
The apparatus of decomposition consists solely of the organ 
of generation ; for no other glands exist in any genus of this 
group. ‘There are several distinct sorts of it, since it is some- 
times composed of female and male parts separated on dif- 
