30 EMBEYOLOGT. 



KoUiker. Die Bildung der Samenfadeu in Blaschen. Denkschr. d. Sohweizer. 



Gesellsoh. f. Naturwiss. Bd. VIII. 1847. 

 N'ussbauin, M. tJeber die Veranderungen der Geschlechtsproducte bis zur 



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

 Reicliert. Beitrag zur Entwickelungsgesohiclite der Samenkorpercben bei 



den Nematoden. Miiller's Arobiv. 1847. 

 Seli-weigger-Seidel. Ueber die Samenkorpercben uud ihre Entwicklung. 



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

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



Lebre 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. Ban und Entwicklung der Samenfaden. Anat. Anzeiger (1887), 

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



CHAPTER II. 



TBE 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 fertihsed they must first 

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

 the phenomena of maturation. 



The maturation-phenomena begin v^ith 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 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. 12.4), in that fiuid escapes 

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

 and the germinative dot becomes indistinct and breaks up into small 

 fragments (fig. 12 5 hf). During this degeneration of the germinative 

 vesicle a nuclear spindle (fig. 12 .8 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 sjjindle (fig. 12 .B sp), — a form 



