626 



THE AMERICAN NATURALIST [\ ol. XLI 



of measurements to which it refers. For here we find that the 

 smallest number of whorls (6) is found in shells from the greatest 

 depth (920 m.) while a littoral specimen has the largest number 

 (9) except one which has ten volutions and was obtained from a 

 depth of 740 meters. Judging by the actual number of whorls, 

 there appears to be nearly a steady increase in the number from 

 920 meters to shallow water. ^Moreover, it does not appear from 

 Sturany's table how he eliminates differences in age in the individ- 

 ual measured. Taking shells of the same number of volutions (8) 

 and therefore presumably of the same age, we have for 

 920 meters in depth — a length of 73 mm. 

 920 " " " " " " m\ " 

 612 " " " " " " 4ll " 

 212 " " " " " " 57 " 

 Subtracting the length of the spindle we have in the same speci- 

 mens the following height of spire of 8 volutions. 



920 meters in depth a length of spire of 35 mm. 

 920 " " " " " " '* " 27 " 

 612 " " " " " " " " 22 " 

 212 " " " " " " " " 23^ " 

 the greatest variation being within ihv saiiu' depth. Since the 

 number of volutions is here the same, this (lillVieiice in height can 

 only be ascribed to a difference of embnu inii- in the earlier whorls. 

 A detailed description of this difference would have been of extreme 



valuable than the tabulation of lengths and numbers of volutions, 

 which without further discussion are of very little significance and 



somewhat larger size of the initial whorl, or the relative number of 

 whorls, this diflVrenee may very well l)e regarded as due to the 

 difl'erenee of envin.nnu>nr." That the envin.nineni may indnence 

 the devel(,,>nient by retanling or aecqeratin- it. seems hardly 

 (luestionable. and that as the result of such retardation or aeeeU'ra- 

 tion the eirrnint'ereiu iai ui-owfli of the original shell may inci'ease 

 proportionately more lapidly than the spiral growth, thus pro- 

 ducing a larger initial whnrl, i> also (•onij)rehensible. As is shown 

 by stu(hes of the enibiyonic de\ elopinetit of I'lihjur carica and 



