OF CONCHOLOGY. 271 



e 



Ill's own. I would remark, by the waj, that the size of the lat- 

 ter differs in different individuals of the same species, or perhaps 

 in the same individual at different times. The orifice of the anus 

 is simple, but, in most species, a number of subcylindrical pa- 

 pillae or tubercles are noticeable inside of it. The latter part of 

 the rectum in Acmcea is repeatedly constricted, so that the fseces 

 are expelled in sausage- shaped pellets. The renal organ, as 

 shown by Lankester, is double ; one of the two sacs, however, is 

 nearly abortive, and seems almost imperceptible in some species 

 of Collisella. These sacs empty by two papilUie, in Patella, one 

 on each side of the anal tubercle ; in Collisella there is no pa- 

 pilla to the left of the anus, but a non-elevated, simple, very mi- 

 nute orifice, sometimes much further (to the left) from the anus 

 than the papilla on the right side. Cuvier does not mention the 

 left hand one in the text, but it is represented on the plate in its 

 proper place (fig. 8, pi. 2). 



I have not been able to have access to the paper of MM. 

 Robin and Lebert, who have noticed the generative organs. Mr. 

 Lankester gives some particulars in regard to them. The ovary 

 has been frequently mentioned, and I have elsewhere described 

 the male gland of Collisella. The oviduct mentioned by Cuvier 

 seems to be wanting, though I have several times thought that I 

 detected a slender, exceedingly thin duct proceeding from the 

 extreme left of the gland and opening into the dendritic renal 

 sac. I cannot say that I feel sure of this, hoAvever, as the con- 

 dition of the specimens was unsatisfactory, from the spirit in 

 which they were preserved. There does not appear to be any 

 other opening through which the young can be extruded, and I 

 am inclined to believe that some such duct exists and will even- 

 tually be demonstrated. If the " capito-pedal orifices" exist, 

 they must be far too small to admit of the extrusion of the young 

 mollusk with its shell, as described by Fischer. 



To the latter naturalist we owe the whole of our very slender 

 knowledge of the development of Patella. He found the ovaries 

 filled with young moUusks in the month of March, and in April 

 the rocks and the parent shells were covered with a multitude of 

 young Patellne, about one millimetre in length. This disproved 

 the idea that the eggs were deposited in a single mass, and 

 showed that the method of extrusion rather resembled that of 

 Chiton. 



It is extremely desirable that the development of this animal 

 should be observed from its early stages, and after that, it is to 

 be hoped that some careful anatomist will give to the world an 

 account of the anatomy, on the plan of Mr. Hancock's magnifi- 

 cent paper on the Brachiopoda. It is by no means impossible 



