No. 2.] COMPARATIVE CVTOLOGICAL STUDIES. 



561 



EXPLANATION OF PLATES XXI-XXX. 



All the figures have been drawn with the aid of the camera lucida, and rep- 

 resent sections of the structures deUneated. Those parts of them which are 

 colored represent as accurately as possible the stained preparations from which 

 they were copied ; in most of the figures only certain portions are colored, the 

 other details being filled in with the pencil. In order to show the correct pro- 

 portionate size of the various cells and nuclei the greater number of the figures 

 have been made at a magnification afforded by the homogeneous immersion lens 

 j'j of Zeiss, with the ocular 4, and unless otherwise specified this may be under- 

 stood to have been the magnification employed. The following abbreviations have 

 been used in the figures : 



