4oS 



GA ULE. 



[Vol. A^II. 



They are more numerous in the male than in the female 

 spleens. Since they are principally seen enclosed in the 

 *' nurse" cells, it is not essential to compare their curves 

 with those of the other elements of the spleen separately. 



fa § 



•^ -=> 





3 fi ■? ■" 3 

 & t; 2 > o 



<; w o ^ Q 



g. Pigment Curves. 



The general conclusion from these curves is that there is 

 more pigment in the spleen in winter than in summer. There 



is less pigment in the spleen 

 Rana Temporaria. during the period of copulation 



than immediately before or after 

 this act. The esculenta spleens 

 have more pigment than the 

 temporaria spleens, the males 

 less than the females. Small 

 spleens contain comparatively 

 more pigment than large 

 spleens. Spleens containing a 

 large proportion of blood are 

 poor in pigment. There is 

 little pigment in spleens con- 

 taining many follicle cells. 

 The cytozoa and pigment 

 curves combine to make the 

 " nurse " cell curves, since the 

 cytozoa and pigment are a pro- 

 duct or element of the "nurse" 

 cell. The predominating color 

 of the pigment in the escidenta 

 spleen is yellow, the black pig- 

 ment, however, exceeds the yellow in the male spleen in 

 the month of May. The predominating color of the pig- 

 ment of the teviporaria spleen is yellow in the summer, yellow- 

 grey in winter. Black pigment predominates at the end of 

 the food-period, and in the male spleen in May. 



15 



10 



E 



I 

 



15 



10 

 6 

 



Rana 



Esculenta 



Fig.f. — Cytoaoa Curves. 



