454 BULLETIN 10 0, UNITED STATES NATIONAL MUSEUM 



The type (U.S.N. M. no. 313722), collected on Sibolon Island by 

 Mr. Canonizado, has 5 whorls and measures: Length, 27.3 mm; 

 greater diameter, 27.9 mm; lesser diameter, 22.5 mm. 



This species strongly suggests Cochlostyla (Cochlodryas) halichlora 

 Semper, from Luzon, but is in every way much smaller. 



Subgenus Prochilus Albers 



In this subgenus the shell is of small to medium size, of ovate, 

 elongate-ovate, or ovate-conic form, and covered with a thin shining 

 periostracum, which may or may not be hydrophanous. The base is 

 usually narrowly perforated, although often the perforation is covered 

 by the reflection of the inner lip. The peristome is broadly expanded, 

 thickened, and reflected. 



Type: Cochlostyla (Prochilus) virgata (Jay). 



THE COCHLOSTYLA (PROCHILUS) VIRGATA (JAY) COMPLEX 



Here and there, the world over, the field naturalist meets with 

 problems of a most puzzling character. While in most instances he 

 finds that organisms belonging to what we call a species reproduce 

 themselves with their definite characters so faithfully that they are as 

 easily recognized as the coins of a modern realm, nevertheless he now 

 and then meets with an assemblage of specimens that occupy a definite 

 habitat but, while they have certain characters in common that have 

 caused naturalists to assign them as a species to a particular genus, 

 present such an enormous range of variations that it is difficult to find 

 two individuals exactly alike. Not infrequently he even finds indi- 

 viduals among such a group that might be assigned to a widely different 

 species, if general resemblance only were considered. 



Long ago groups of this kind were said to be in a state of flux, and 

 more recently they have been said to be mutating, and the individual 

 variants have been called mutants. Speculations as to the origin 

 of these mutants have been many, and the literature of today is still 

 filled with diverse concepts of this problem. 



Personally, I believe that my Cerion breeding experiments have shed 

 considerable light on the molluscan phase of mutants. Crossing 

 Cerion viaregis Bartsch with Cerion incanum Binney produced in the 

 F 1 generation offspring that fused in shell characters the features of 

 the two parents, while the F 2 generation produced an endless array of 

 mutants, varying enormously in size, color, sculpture, the structure of 

 the soft anatonry, in fact, simply running riot as far as variation is 

 concerned. Here then we have an explanation of a source of mutation. 



What I have said regarding the Cerion viaregis and Cerion incanum 

 hybridization experiments is duplicated in the field on the north coast 

 of Cuba between Habana and Matanzas, where at the west end of a 



