CONCHIFEBA. 



paratus ; or perhaps it would be more strictly in accordance with 

 what is known concerning their mode of reproduction to say that 

 they are all females ; no organ that can be regarded as belong- 

 ing to a male system having, as yet, been pointed out.* 



The ovary, which in fact is the only viscus distinguishable as 

 being connected with the propagation of these animals, is generally 

 a wide glandular sacculus, occupying a considerable portion of the 

 visceral mass. In the Oyster it is, when full of spawn, largely 

 spread through the body ; and if at such seasons its delicate walls 

 are ruptured, countless ova of microscopic dimensions escape from 

 the lacerated part. In Pecten the ovary is very conspicuous from 

 the brilliant colour of the eggs contained in its interior ; it con- 

 stitutes the greater part of the bulk of that prominent tongue-like 

 organ which projects between the branchiae (fig. 176,/) : or, in 

 genera where the foot is very largely developed, as in Cardium 

 rusticum, a great part of the base of that organ is hollowed out 

 into a capacious cavity, enclosed by its muscular walls, wherein 

 the delicate folds of the ovarium (Jig. 182, a) are partially em- 

 bedded, together with a portion of the intestinal canal (c). 



(428.) The course of the oviduct has not as yet been satisfac- 

 torily traced, and, consequently, the precise passage by which the 

 eggs are excluded is still a matter of discussion. There is, how- 

 ever, one very remarkable arrangement observable connected with 

 the reproduction of conchiferous Mollusca, the object of which 

 is sufficiently evident. 



When we consider the position of the ovary in these bivalves, 

 placed as it is in the substance of the body, and reflect upon the 

 immense numbers of eggs to which they give birth, for thousands 

 of ova are generated by every one of these prolific beings, we 

 perceive that, without some special provision, the imprisoned animals 

 would, when gravid, be seriously inconvenienced and exposed to 

 continual danger, as the inordinate enlargement of the ovary would 

 preclude the possibility of bringing the valves of the shell in con- 

 tact with each other. In order to obviate the difficulty referred 

 to, the ova are expelled from the ovarian nidus in an immature 



* At a late meeting of the Zoological Society, a communication from M. Rudolph 

 Wagner was laid before the meeting, from which it would appear that that gentleman 

 has satisfied himself that in many of the lower classes of animals hitherto regarded as 

 being Monoecious, as for example, in many tribes of Polyps, Acalephae, Tunicata, 

 Conchifera, and Gasteropoda, in some individuals the organ generally looked upon as 

 being an ovary, contains Spermatozoa, or Seminal Animalcules j and thus there is reason 

 to suppose, that in such species a difference of sex exists, and that there are males 

 which supply a fecundating secretion. 



