98 STERELMINTHA. 



Distoma hepaticum already given (Jig. 38). On comparing the two 

 we are at once struck with the superior concentration of all the 

 systems of the body, visible in Distoma perlatum. The ali- 

 mentary canal (Jig. 42, ) commences, as in the former example, 

 by an aperture situated in the oral sucker ; but, instead of ramifying 

 through the parenchyma of the body, is contained in an abdo- 

 minal cavity, in which it floats in common with the other viscera. 

 The oesophagus (a) is a simple flexuous tube terminating 

 abruptly in two lateral and more capacious intestines, (b, b,) 

 terminated by blind dilated extremities, which form the digestive 

 apparatus. 



Two vascular canals (d, d) are seen on each side of the body, 

 which ramify extensively, but of these the principal trunks only 

 are represented. 



(131.) The Distoma perlatum is allied to the STERELMINTHA in 

 the hermaphrodism of its generative organs, and the parts subservient 

 to reproduction will be found analogous in structure and arrange- 

 ment to what we observed to be the usual conformation in that 

 order. The ova would seem to be produced in the parenchyma 

 of the body, as in the fluke ; from this situation they are con- 

 veyed by two canals (e) into a capacious receptacle (/), from 

 which arises the tortuous oviduct (g), represented in the en- 

 graving distended with eggs. Near its termination the oviduct 

 is joined by two secerning vesicles having their interior appa- 

 rently of a villous texture. These vesicles are regarded as 

 being the testes, and are supposed to pour out an impregnat- 

 ing secretion, by which the ova are rendered fertile as they 

 pass out of the body. The external aperture through which 

 the eggs are discharged is placed upon a prominent tubercle 

 (t), which, if mutual impregnation is essential in these animals, 

 may indeed perform the office of an intromittent instrument. 



