318 



BULLETIN: MUSEUM OF COMPAKATIVE ZOOLOGY. 



EXPLANATION OF PLATES. 



The various magnifications and the means of obtaining them are shown in the 

 following Table : — 



Projection of the image was made by an Abbe camera lucida. All of the figures 

 except 95 and 90 were drawn from single sections. Figures 1-18 (Plates 1-3) were 

 taken from eggs before deposition ; Figures 19-81 (Plates 4-13) after deposition. Of 

 the photomicrographs (Plates 10, 11) Figures 67, 68, 69, and 79 were made with a 

 Zeiss microscope and 4 mm. lens, employing a Zeiss horizontal photomicrographic 

 camera. Magnification, 670 diameters. Tlie negatives of Figures 65, 66, 70-78, and 

 80 were taken by E. L. Mark and L. J. Cole after the excellent method devised by 

 Foot and Strobell (:02), on Carbutt "process" plates with Zeiss 2 mm. homog. im., 

 objective and compensating ocular No. 4. Magnification, 670 diameters. 



ABBREVIATIONS. 



c7. . 

 c'pl. . 

 c'so. . 

 fus. c. 

 pronl. ? 



Centriole. 

 Centroplasm. 

 Centrosome. 

 Central spindle. 

 Female pronucleus. 



pronl. <f 

 St. ctx. . 



St. med. 

 vsl. chr'so. 



Male pronucleus. 

 Cortical layer (stratum 

 corticalis). 



Medullary layer. 



Chromosome vesicles. 



