SO EMBRYOLOGY. 



Kolliker. Die Bildung der Samenf iiden in Blaschen. Denkschr. d. Schweizer 



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

 Nussbaum, M. Ueber die Veriinderungen der Geschlechtsproducte bis zur 



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

 Reichert. Beitrag zur Entwickelungsgeschichte der Samenkorperchen bei 



den Nematoden. Muller'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. Spermatologisc.be Beitrage. Archiv f . mikr. 



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



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

 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 invertebrated animals, such as the 

 Echinoderms and Nematodes (the ni.-i \v-worin 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 tin- description 

 towards its surface, shrivels a little (fig. 12.4), in that fluid escapes 

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

 and the germinative dot becomes indistinct and break* uj into small 

 fragments (fig. 12 B Iff). During this degeneration of the germinative 

 vesicle a nuclear spindle (fig. 1 '-' H Kp) is formed, as can be recognised 

 only after appropriate treatment with reagents : there arises out of 

 </ ///,- </'///' -nut ire dot, or out of a part of the nuclear substance 

 of the germinative vesicle, a nuclear spindle (fig. 12 B sp), a form 



