50 EXPERIMENTS IN THE BREEDING OF CERIONS. 



colony upon this key, we would treat the material as we have treated 

 such assemblages in the past; that is, as a very variable species. It 

 therefore seems proper to assume that the converse should receive an 

 equally favorable consideration, for it seems fair to believe that further 

 breeding experiments will prove that such complexes are the product 

 of cross-breeding. 



The two species which have crossed here are very remotely related 

 as can be readily seen by a comparison of plates 7, 8, 9, which represent 

 the check series of Cerion viaregis from Bastian Point, Andros, and 

 plates 54, 55, 56, which represent a check series of Cerion incanum — 

 Cat. No. 334726, U. S. N. M.— from Porgee Key, Florida. The 

 last-mentioned species is known to inhabit many of the keys from 

 Virginia Key southwestward to the Marquesas Keys. A comparison 

 of the anatomic structures shows even more striking characters of diver- 

 sity, as shown on plates 1, 5, and 6, and discussed on pages 7 to 13 of 

 this paper. The fact is, that it is very surprising that organisms pre- 

 senting such great differences in organization should be able to cross 

 at all, and it is still more remarkable that they should have produced 

 fertile crosses. In this connection it should be recalled that oiu: efforts 

 to effect a cross between the Bahaman Cerion casablancoe and Cerion 

 maregis proved unsuccessful. 



The offspring produced by this crossing show a remarkable range in 

 variation, as can be readily seen by an examination of the 125 figures 

 on plates 57, 58, and 59. This variation not only includes forms which 

 appear near tjrpical Cerion incanum and near typical Cerion viaregis 

 and all grades of intermediates between these, but also forms that so 

 closely resemble species of the Bahama mottled Cerion of the Cerion 

 martensi group, that one not knowing their origin would unhesitatingly 

 refer them to species of this complex occupying restricted areas in the 

 Bahamas. Our crossing has evidently called to the sm-face submerged 

 mottled Cerion strains present in Cerion maregis and probably present 

 in all the members of the complex that has been passing under the name 

 of Cerion glans. 



The mixed elements vary in shape from the slender Cerion incanum 

 type to the more or less cyUndric Cerion viaregis, but a few of the speci- 

 mens diverge entirely from this shape and assume the outline of the 

 mottled Bahama Cerions. In ribbing they vary from the almost 

 smooth Cerion incanum to the strongly costate Cerion viaregis. Forms 

 having the shape of Cerion incanum may have the sculpture of 

 Cerion maregis, or the reverse may obtain. It should be mentioned 

 here that the ribbing in the Bahama mottled Cerion falls between 

 Cerion incanum and Cerion maregis as far as strength goes, usually 

 being a little nearer Cerion incanum in this respect. In coloration these 

 specimens range from the color of Cerion incanum, which is white or 

 sometimes finely vermiculated, to variously mottled, blotched, streaked 



