EXPERIMENTS IN THE BREEDING OF CERIONS. 33 



tion which exceeds by 1.2 mm. any found in the check series or in the 

 first generation. Cerions are fairly variable in measurements, as 

 shown in our series, and this one large exceptional specimen does not 

 really mean anything in this instance. 



The greatest diameter presented by any specimen of the second 

 generation is a little less than that presented by any member of the 

 check series or the first generation. When it comes to the least meas- 

 urement we find that in the number of whorls the second generation 

 has given us a specimen with 8.4 whorls, which is less than that pre- 

 sented by any form of the check series or the first generation. In the 

 altitude measurements, too, we find one specimen with 17.3 mm., 

 which is considerably less than the altitude of the two other groups, 

 while in the measurement of the diameter the least diameter shown by 

 any specimen of the second generation is slightly greater than that of 

 the check series or the members of the first generation. However, 

 it is perfectly safe to say that all the variations presented by the 

 Florida-grown first and second generation specimens do not speak 

 for any material change having taken place within this group. I feel 

 perfectly confident that all the variations presented here are entirely 

 within the range of Cerion viaregis as it occurs at Bastian Point. This, 

 then, means that the changed environment to which we have subjected 

 these organisms in transplanting them to Florida has not affected 

 them in such a way as to produce such differences as one observes 

 between the various colonies in the Bahamas. That is, that Cerion 

 viaregis seems to be quite stable within its normal limits of variation 

 and appears to adhere to these limits even when subjected to a decidedly 

 changed environment. 



Cerion casablanc^ Bartsch. 



Of this species 100 specimens have been taken at random from a lot 

 collected in the White House region on Andros. Figures of these are 

 given upon plates 32-34. Their measurements are shown in table 16. 

 These specimens are entered as Cat. No. 334723, U. S. N. M., and No. 

 13 is selected to serve as type. 



The Colony on the First Ragged Key North of Sands Key. 



On this key 500 specimens of Cerion casablancce were planted in June 

 1912, on a sandy ridge on the middle of the outside of the key. Here 

 we have a fringing element of bay cedar to the seaward, as well as on the 

 inner margin of the dune. The dune itself contains a sparse growth of 

 Sporoholus virginicus, some Hymenocallis, and a very dense matting of 

 Sesuvium portulacastrum. 



On April 25, 1913, we found most of the planted specimens attached 

 to the stems and leaves of the succulent Sesuvium; they seemed to be 

 thriving in this new habitat. We also discovered 3 young shells having 

 1.3, 1.5 and 2 postnuclear whorls respectively. 



