THE OSTEACODA. 



261 



curves, in the cabsence of marked morphological differentiation. The mean of 14 males 

 at Stage II. measured to the second place was 0"76 mm., which seems to show that the 

 curve, the apex of w hich is at 0'7, contains the materials of tM'o curves. 



The actual measurements from Avhich the curves in fig. B liavo been plotted are as 

 follows : — 



Table D. — Total specimens measured: 124 ^ +76 S =200. 



It being impossible to get a satisfactory mean of the lengths, owing to the overlapping 

 of the curves, it is worth notice that the modes of the curves of the (supposed) three 

 oldest stages correspond to Brooks's law as well as could be expected : — 



Males: growth-factor, 1'42. 

 0-50 X 1-42 = 0-71 

 0-71 xl-42 = l-00 



Females: growtli-laclta. 

 0o0xl-40 = 0-70 

 0-70xl-40 = 0-98 



Until a more accurate method of measurement for these minute specimens has been 

 devised, this approximation will have to serve. 



Fis. B. 



40 30 20 10 10 ?0 30 



-r n 



CONCHCECIA DAPHNOIDES, ClaUS, 



The best method of measurement for this species required consideration, because the 

 contoiu' of the shell is so utterly different from that of the other species handled. 



43* 



