86 



STEEELM1KTHA. 



Fig. 37. 



the central portion of this ramified ovary issues a wide canal or 

 excretory duct (c), which may be traced to a prominent tu- 

 bercle placed on the lateral 

 margin of every segment (e), 

 where it terminates in a mi- 

 nute pore opening externally. 

 This canal, which may be 

 called the oviduct, is seen 

 just before its termination in 

 the external pore to be joined 

 by a delicate tube (d), which 

 appears as a dark line under 

 the microscope, and derives 

 its origin from a small bulb or 

 vesicle, and may be regarded 

 as most probably furnishing a 

 secretion serving to fertilize 

 the ova prior to their expul- 

 sion ; such, at least, is the 

 office generally assigned to it. 



Many thousands of eggs must be produced from such multiplied 

 sources of reproduction ; and yet how are they preserved and 

 replaced in circumstances favourable to their developement ? 

 Fortunately it is rare to meet with more than one of these 

 creatures at the same time, taking up a residence in the same 

 individual ; and, in fact, the species which has been specially the 

 subject of our description is often called, par excellence, " the 

 solitary worm," from this circumstance. Yet what becomes of 

 the reproductive germs furnished in such abundance ? Do they, 

 as was the opinion of Linneus, live in a humbler form in stagnant 

 waters and marshes, until they are casually introduced into the 

 body of some animal, where, being supplied profusely with food 

 and placed in a higher temperature, they attain to an exuberant 

 developement ? Or are the germs thus numerous in proportion to 

 the little likelihood of even a few of them finding admission to a 

 proper nidus ? To these questions we can only reply by conjec- 

 tures ; and, interesting as the subject is, few are more entirely 

 involved in mystery. 



(118.) In the Fluke, Distoma (Fasciola, Linn.) hepaticum, we 

 have an entozoon of more complex and perfect structure ; one of 

 those forms, continually met with, which make the transition from 



