428 Dr. J. E. Gray on the genus Assiminia. 



I adduced as one of the reasons proving that Assiminia is not 

 a TruncatellOj that it had not the white pupil which Mr. Clark 

 has shown to be one of the characters of the group ; on which 

 Mr. Clark obsen- es, " I do not understand the logic of this ; the 

 point in question is a mere specialty ; one may with as much 

 reason say that a man with a red iris or pupil_, for example an 

 albino, is not of the genus Man, because he has not the usual 

 dark or grey iris; so, it is equally absurd to infer that A. Gray- 

 ana is not a Timncatellay because the white iris or pupil was not 

 detected.^^ Surely Mr. Clark must know the difference between 

 an accidental lusus, like an albino man or woman, and a cha- 

 racter common to all the specimens of a species, and all the 

 hitherto-observed species of a group. The argument objected to 

 may be " illogical " and " absurd," though I own that I do not 

 think it so ; but at any rate I am not answerable for its use, 

 for in Mr. Clark's 'MoUusca/ p. 386, occurs the following 

 passage, referring to Truncatella atomus : " moreover, the eyes in 

 the dried animal are perfectly visible, and show the charac- 

 teristic white pupil of what may now be safely termed its con- 

 generJ' 



In explanation of Mr. Clark's pertinacity on this head, we 

 must bear in mind that his character as a soothsayer or prophet 

 is dependent on his proving that Assiminia is a Truncatella ; for 

 before he had seen the animal, at page 385, and again at page 

 521 of his ' Mollusca,' he predicts, " that when the animal is 

 better known, it will belong to the latter genus." 



This is a good illustration of what I consider one of the prin- 

 cipal defects of IVIr. Clark's work. From some important ob- 

 servation, or from some a-priori theory, he picks up a crotchet, 

 such as that the water does not enter by the lower siphon of 

 the Bivalves, that the teeth are not good generic characters, that 

 all the animals with a multispiral operculum are unisexual, &c., 

 &c.; and forthwith he proceeds to examine specimens, appa- 

 rently not with the desire to discover if the idea is founded in 

 fiact, but to prove the truth of it ; and it is astonishing how his 

 power of obser\'ation appears to adapt itself to his preconceived 

 theory, and enables him to see just what he wishes, though to 

 other observers the facts are clearly contrary. In the same 

 manner, it appears to me that when he reads a work, some of 

 the observations of the author seem to take possession of his 

 mind, and after a time he appears to forget that they are not 

 founded on his own observations, and puts them forth as his 

 own discoveries. Thus his new system itself is (unwittingly 

 perhaps) only copied from the works of Blainville and Leach, 

 and his referring the genera ISkenea and the elongated Cerithia 



