THE EGG OF THE DOMESTIC CAT 165 



Pro7iuclei 



All of the small number of fertilization stages studied after 

 having been preserved were in about the same condition. Both 

 pronuclei were compact and very deeply stained (fig. 12). At the 

 next stage, fusion had taken place in the center of the egg in a 

 region of clear protoplasm, the deutoplasmic globules having 

 moved toward the periphery. The chromosomes only are dis- 

 cernible, no evidence being noted of the presence of spindle fibres. 

 The chromosomes differ from those of either of the polar spindles, 

 being filiform in shape, with enlarged extremities. 



Cleavage 



In the two-celled stage there are usualh^ found two peculiar 

 bodies which stain dark blue with Delafield's haematoxylin and 

 brown with Heidenhain's iron haematoxylin. They are variable 

 in size, shape and location, are irregular in outline, and of a more 

 or less granular texture. Very similar smaller bodies in number 

 up to a dozen or more are sometimes found in ovarian eggs near 

 the end of the period of growth. 



Two-celled stages are surrounded by a zona which is of vari- 

 able thickness. Sometimes it shows only at special points such 

 as those where it covers the polar bodies, or where the egg outline 

 is indented, as at the margin of the cleavage plane. At other 

 times it is well in evidence (fig. 13) and shows as clearl}^ as in 

 mouse eggs for example. 



In conclusion, the writer welcomes this opportunit}' of ex- 

 pressing his obligation to Professor W. R. Coe for advice and 

 encouragement which have been freely given and for the inspi- 

 ration originating in his rigorous but kindly criticism. 



