SMITHSONIAN EXPLORATIONS, 1 927 55 



Curasao, Ccrioii crassUahrc from Porto Rico, of which we have 

 also had two generations of Florida grown offsjMnngs. While these 

 took four years for development, they told the same story presented 

 hy the Bahama Cerions, namely, that they did not respond to changes 

 in environment in these two generations. A numher of other forms 

 have since been added and are being subjected to the same critical 

 tests. 



On the Newfound Harbor Key in the Florida Key chain, we mixed a 

 colony of Ccrioii viarcgis with native Florida Ccr'wn iticanum, and 

 great was our surprise to find three years later a hybrid between 

 these two species. This was the more startling because the Florida 

 group is not represented in the Bahama Islands, and its ancestors 

 are traceable on the Florida Keys back to Oligocene times. The 

 cross therefore was one of very distantly related things, and the 

 specimens secured of the first generation of this cross were true 

 hvl)rids showing intermediate characters between the two in about 

 equal proportion to the two ancestors, and very uniform in appear- 

 ance. The second generation of this hybrid group, however, was a 

 surprise, for now an endless number of mutations appeared, cover- 

 ing almost everything in the field of Cerions except spiral sculpture. 

 There is a tremendous difference in size, general shape, sculpture, 

 and coloration in the various individuals. 



This finding reminds one very much of De Varies' Oenothera prob- 

 lem, the basis of his mutation theory, due to a similar hybridization 

 cause, and also that presented by certain of the more recent experi- 

 ments on insects, and caused us to attempt the crossing of individual 

 pairs of Cerions instead of the mass reaction as featured by the New- 

 found Key colony. For this jiurpose. cages were employed at first. 

 The fine meshed screen of these cages, however, intercepted the 

 formation of dew within the cages, which in turn apparently reacted 

 on the food suppl}- as well as the moisture supplv of the Cerions, and 

 resulted in killing" them. The making of islands was then resorted 

 to, and we have at the present time a series of small islands en- 

 closed by trenches which are kei)t filled with water and serve as a 

 barrier across which our mollusks will not pass. On these islands as 

 well as in cut down cages — mere board enclosures with a strip of 

 monel metal wire l)ent inward, tacked to the upper free edge of the 

 boards, which leaves the central portion of the cage exposed to the 

 normal atmospheric conditions — pairs of Cerions have been planted 

 in the hope of obtaining the desired individual cross. These studies 

 are going on at the present time. ■Meantime we have dissected too 

 of the hvbrids from the Newfound Harbor colon^■, and found most 



