14 



TEXT-BOOK OF EMBRYOLOGY. 



Acrosome 



Head 



Anterior end knob 

 Posterior end knob 



Main segment 

 of tail 



seen on edge, it is pear-shaped, the small end being directed forward. It 

 consists mainly of nuclear material derived from the nucleus of the parent cell. 

 (See Spermatogenesis.) A thin layer of cytoplasm, the galea capitis or head- 

 cap, envelops the nuclear material, while in 

 front there is a sharp edge known as the 

 apical body or acrosome. In contrast to the 

 nuclear portion of the head, which of course 

 takes a basic stain, the acrosome stains with 

 acid dyes. In some forms the acrosome is 

 much larger than in man and extends 

 forward from the head-cap as a long spear, 

 sometimes barbed — the perforatorium. This 

 process perhaps assists the spermatozoon in 

 clinging to or in burrowing its way into the 

 ovum. Many peculiar types of perfora- 

 toria, for example, lance-shaped, awl- 

 shaped, spoon-shaped, corkscrew-shaped, 

 have been described and have given charac- 

 teristic names to the spermatozoa possessing 

 them. 



2. The body in the human sperma- 

 tozoon is cylindrical and about the same 

 length as the head. It consists of a deli- 

 cately fibrillated cord, the axial thread, sur- 

 rounded by a protoplasmic capsule. In 

 some forms (Mammals) a short clear por- 

 tion, the neck, unites the head and body. 

 In the neck there can sometimes be demon- 

 strated an anterior end knob and one or 

 more posterior end knobs to which is attached 

 the axial filament. In man and in some 

 other forms, delicate fibers — spiral fibers — • 

 wind spirally around that portion of the 

 axial filament which lies within the body. 

 At the posterior end of the body, the axial 

 filament passes through the end disk or end 

 ring. 



3. The tail in the human spermatozoon is forty to fifty microns in length; 

 is the direct continuation of the axial thread of the body; and consists of a main 

 segment thirty-five to forty-five microns in length, and a short terminal 

 segment. As in the body, the axial filament is delicately fibrillated. Sur- 



FlG. 8. — Diagram of a human sperma- 

 tozoon. Meves, Bonnet. 



