OP THE OYSTER, MOSSEL, AND COCKLE. 15 



progress, is very great, although, doubtless this fact led to the 

 early assertion that it was truly hermaphrodite from the presence 

 of easily recognized eggs with bundles of spermatozoa in the same 

 gland. But in the cockle and mussel we have to imagine the dis- 

 charge of spermatozoa into the water, or mud and sand, to be 

 taken up by the genital orifices of other creatures and distributed 

 throughout their very complex glands — a very difficult thing to 

 imagine, I think. But supposing this mechanical difficulty not 

 insuperable, evidence, I think, ought to be furnished of this influx 

 of spermatozoa into the glands of animals containing eggs. I 

 may mention also that the gradual change in colour of the glands 

 of the creatures points in the same direction. In mussels especially 

 this variation of shade from pale creamy white to a rich orange is 

 very noticeable. I have not examined the Anomia mentioned by 

 Professor Owen in the extract I read, but I was struck with its 

 truth in reference, we will say, to a bed of mussels. Roughly 

 examining any number, seeking for the presence of spermatozoa or 

 eggs, you would probably find a nearly equal number of animals 

 containing each, but the intermediate stage would require a much 

 more thorough examination to discover. The fact of the aggrega- 

 tion of these animals in beds has been accounted for as a wise 

 provision of nature, to allow of the easy access of spermatozoa to 

 the females of these anchored mollusks, and the transmission of 

 spermatozoa by water has been compared to the transmission of the 

 pollen of plants by the air. I think the fact might be more reason- 

 ably accounted for by the limited power of motion in the young, and 

 by the fact that the places in which they are found are suited to 

 their requirements in the important matters of food and tempera- 

 ture. I will now conclude, gentlemen, hoping that you will deal 

 leniently with me in the matter of criticism, and that your 

 remarks may furnish me with facts about the three mollusks to set 

 me right where I am wrong, and to help me in any future 

 investigations.* 



EXPLANATION OF PLATE II. 

 The plate attached to this paper gives, as far as possible in ao limited a space, 

 a concise history of the changes in the generative glands of these creatures, from 



* The lateness of the hour at which the above paper was read precluded any 

 discussion upon it. Dr. Moore has promised a further paper upon this very in- 

 teresting subject, in March or April — a suitable time to commence practic.il 

 observations. This paper will have special reference to the supposed larval forms 

 of the Cockle and Mussel.— Ed. J. Q. M. C. 



