72 SEX AND HEREDITY 



Birds that we find complete emancipation from the watery 

 environment. The successful attainment to this has 

 been rendered possible partly by the development of a 

 horny impermeable skin in the adult, and partly by 

 modifications in the reproductive processes. It is the 

 latter alone which concern us now. 



FIG. 41. 



Nototrema pygmaeum, female. The eggs, large in size and few in number in this 

 species, are seen showing through the roof of the pouch in which they are contained. 



In the Bird the female gamete or macrogamete, or 

 egg is of relatively enormous size a spherical cell, 

 packed with reserve food-material or yolk, food-hoarding 

 having here reached its maximum. It is what in domestic 

 language is called the yellow or " yolk " in the case of 

 the Hen's egg. 



The act of syngamy the fusion together of male and 

 female gamete takes place within the body of the bird > 



