CYPREA. 83 



in the construction of the Univalves, the whorls 

 increase in magnitude as they advance transversely 

 from the apex, and receive no increment after the 

 perfect aperture is formed. This bespeaks a limit 

 in the growth of the inhabitant, at which he is 

 taught by instinct to finish off his work. If, there- 

 fore, for any reason, upon which from ignorance 

 we cannot argue, these slugs do quit their shells, 

 it is not, surely, on account of an anomalous ex- 

 cess of bulk. A remark which has been made bi 

 the author, whether justly or not will hereafter be 

 decided, would seem to favour a very opposite 

 opinion. In numberless specimens of the Cypraea 

 exanthema which he has inspected, the thinner and 

 obviously younger shells were, with few exceptions, 

 of large dimensions, whereas the fully ocellated 

 and thicker individuals were considerably smaller. 

 So much difference is there usually in size, that 

 they might be considered as two distinct varieties, 

 were not a progressive course easily obtained, from 

 those having broad bands alone, to those covered 

 with white spots, and totally destitute of bands. 

 This course, however, follows an inverse law with 

 regard to magnitude. The above remark is simply 



