30 



EMBRYOLOGY. 



Kolliker. Die Bildung der Samenfiiden in Bliischen. Denkschr. d. Schweizcr. 



Gesellsch. f. Naturwiss. Bd. VIII. 1847. 

 Nussbaum, M. Ueber die Veranderuugen der Geschlechtsproducte bis zur 



Eifurchung. Archiv f. mikr. Anat. Bd. XXIII. 1884. 

 Reichert. Beitrag zur Entwickelungsgeschichte der Samenkorperchen bei 



den Nematoden. Miiller's Archiv. 1847. 

 Schweigger-Seidel. Ueber die Samenkorperchen und ihre Entwicklung. 



Archiv. f. mikr. Anat. Bd. I. 1865. 

 Valette St. George, von La. Article " Hoden," Strieker's Handbuch der 



Lehre von den Geweben. Engl. trans. New York 1872. 

 Valette St. George, von La. Spermatologische Beitrage. Archiv f . mikr. 



Anat. Bde. 25, 27, 28. 1885, -86. 

 Waldeyer. Bau und Entwicklung der Samenfiiden. Anat. Anzeiger (1887), 



p. 345. (Full list of the literature on Spermatozoa.) 



CHAPTER II. 



THE PHENOMENA OF THE MATURATION OF THE EGG AND 

 THE PROCESS OF FERTILISATION. 



1. The Phenomena of Maturation. 



EGGS, such as have been described in the previous chapter, are 

 not yet capable of development, even if they have acquired the 

 normal size. Upon the addition of mature semen they remain 

 unfertilised. In order that they may be fertilised they must first 

 pass through a series of changes, which I shall group together as 

 the phenomena of maturation. 



The maturation-phenomena begin with changes of the germinative 

 vesicle, which have been followed out the most carefully on the 

 small transparent eggs of invertebratecl animals, such as the 

 Echinoderms and Nematodes (the maw-worm of the horse). The 

 germinative vesicle gradually moves from the middle of the egg 

 the egg of an Echinoderm may serve as the basis of the description 

 towards its surface, shrivels a little (fig. 12 A), in that fluid escapes 

 from it into the surrounding yolk, its nuclear membrane disappears, 

 and the germinative dot becomes indistinct and breaks up into small 

 fragments (fig. 125 &/"). During this degeneration of the germinative 

 vesicle a nuclear spindle (fig. 12 B sp) is formed, as can be recognised 

 only after appropriate treatment with reagents ; there arises out of 

 parts of the germinative dot, or out of a part of the nuclear substance 

 of the germinative vesicle, a nuclear spindle (fig. 12 .Z? sp),- a form 



