TROCHUS. 319 



This is a very unusual position, but it may be the right one, 

 as I think I have seen at its base the point of issue of the vas 

 deferens. Under these peculiar circumstances, how is the 

 necessary contact effected? It will appear below, that there 

 is reason to think all the Trochi are invested with that modi- 

 fication of hermapliroditism which requires mutual congression, 

 as in Helix. 



To support these views, or rather conjectures, of herm- 

 aphroditism, I have to observe, that besides the organ pre- 

 sumed to be the male generateur, which is never absent in the 

 larger Trochi that admit of examination, I have, in numerous 

 examples of T. tennis, T. ziziphinus, and in at least a hundred 

 and fifty T. lineatus, as well as in T. cinerarius and T. umbi- 

 licatus, invariably found the cloven orifice of the matrix placed 

 below the rectum, the canal of which passes partly under and 

 around the sac of viscosity to the ovarium in contact with 

 the liver ; and on the side of that viscus, more posteriorly, 

 there is an elongated, subconical, yellowish-white mass of 

 much firmer consistence, which I take to be the testis. If 

 there be no error in what we have stated, we must consider the 

 Trochi as hermaphrodites, and a transition-group from the 

 Patellida and Helicidce to the strict bisexuals. In addition I 

 may state, that on forty or fifty T. lineatus being immersed in 

 warm water, all discharged a mass of ova, forced from the 

 matrix prematurely. To test this fact, I put as many Litto- 

 rina littorea under similar discipline, and only the females 

 ejected ova. It is necessary to mention that in the minor 

 Trochi, viz. in T. Cutlerianus, T. serpuloides and T. nitens, there 

 is a rather long, flat, smooth filament, which, until the present 

 discovery, I considered a male appendage, horizontally exserted 

 close under the right tentaculum, but which, if the Trochi 

 are hermaphrodites, must be regarded as a kind of feeler, and 

 perhaps of similar nature to that I have observed in the same 

 situation in some of the Rissoa ; but the larger species do 

 not show such .an exserted organ either in a living or dead 

 condition. I am aware that in some mollusca, particularly 

 the Littorina littorea, the organe generateur is much atte- 

 nuated, though not to the extent of obliterating all appearance; 



