W. B. Kirkham — Maturation of the Egg of the White Mouse. 8Y 



Plate VII. 



Figure 14. — Egg in Fallopian tube ; showing second polar body before its twelve 

 univalent chromosomes have been gathered into a solid mass. First polar 

 body has disappeared. At left, within the egg, is seen the sperm nucleus, 

 and above it the separated tail of the spermatozoon ; at I'ight appears tlie egg 

 nucleus, surrounded by delicate radiating fibers. The complete absence of 

 the zona pellucida is in part accounted for by tiie solvent action of the 

 reagents. x 1450. 



Figure 15. — Egg in Fallopian tube ; showing both polar bodies, with their typical 

 differences. Note oval first polar body with its twenty-foiir vmivalent chro- 

 mosomes in a spindle, and the round second polar body with its compact 

 mass of chromatin. The sperm head appears at the left, the female pro- 

 nucleus at the right within the egg. The complete absence of the zona pel - 

 lucida is in part attributable to the solvent action of the reagents, x 1450. 



Plate VIII. 



Figure 16. — Egg in Fallopian tube ; showing first cleavage spindle and second 

 polar body with a resting nucleus. First polar body has disappeared. Note 

 length, and bent form of cleavage chromosomes •, also the distinct centriole 

 ^t each pole of the cleavage spindle, x 1450, 



Figure 17. — Egg in Fallopian tube ; showing two-celled stage. First polar 

 body has disappeared; the second appears above and between the two blas- 

 tomeres. x 1450. 



