|ttotw(tt00itie0 of pttorina flubis, JKatcn, 



By E. EUTHVEN SYKES, B.A. 



HE subject of monstrosities, although a very fascinating 

 one to students of the Mollusca, is one to which 

 very little systematic study has been given. 

 Eecords innumerable, principally, however, of 

 single specimens, have been made of such 

 discoveries, but very little attention has been paid 

 to the causes. Possibly this neglect may be due 

 to the fact that colonies of monstrosities are by no means common, 

 while single monstrous specimens often due to breakage or some 

 such cause are not infrequent. We should notice before coming 

 to our special subject that in all these forms, distorted or otherwise 

 changed as they may be, the nucleus of the shell is in all cases 

 regular. Thus there is no variation from the normal in a univalve 

 until after the embryonic whorls ; then the change takes place and 

 the malformation appears, in some cases increasing more and more 

 with the growth, while in others the animal seems to recover itself 

 and goes back to the normal state. These malformations are not 

 inherited strictly speaking, but I think that an ancestor having 

 become monstrous through external influences (except such as 

 breakage, &c.,) may cause a predisposition in the descendants also 



