SPERMATOGENESIS— INSEMINATION 



167 



Ballowitzi has shown that tlie axial filament is composed of a 

 nnmber of parallel fibrillin, like a muscular fibre. 



Schweigger - .Seidel - and 

 La Valette St. George ^ were 

 the first to prove, independ- 

 ently but almost simultane- 

 ously, that the spermatozoon 

 has the essential character- 

 istics of a complete cell. The 

 head contains the nuclear 

 material, which is sur- 

 rounded by a thin layer of 

 cytoplasm. The end-knob is 

 said to represent the centro- 

 some. 



Spermatozoa, conforming 

 with more or less closeness 

 to the type described above, 

 occur in the great majority 

 of multicellular animals from 

 the Coelenterata up to Mam- 

 mals. In Pisces, and also in 

 Echinoderms, the general re- 

 semblance is very distinct, 

 but in other forms of life 

 there is more diversity in 

 the shape assumed by the 

 spermatozoa. "The head 

 (nucleus) may be spherical, 

 lance-shaped, rod-shaped, 

 spirally twisted, hook-shaped, 

 hood-shaped, or drawn out 

 into a long filament ; and it 

 is often divided into an an- 

 terior or a posterior piece of Fia. .52.— Human spennatozoa on the flat 



different staining capacity, 

 as is the case with many 

 birds and Mammals. The 

 achrosome sometimes appears 



and in pioflle. (Aftei' Bianiman, from 

 Schafer.) x 2500. Those on the right 

 have adhering pi-otuplasm. The tail is 

 only pai'tly shown in the two seen in 

 ])rofile. 



' Ballowitz, " Untersuchungen iiber die Struktur der Spermatozoen," Arch. 

 f. Mikr. Anat., vol. xxxii., 1888, and vol. xxxvi., 1890; Zritxeh. f. ivixs. Zanl., 

 vol. Ix., 1890, and vol. Ixii., 1891. 



^ Schweigger-Seidel, " Uber die Samenkorperelien und ilu'e Entwickelung," 

 Arch. f. Alikr. Anat., vol. i., 1865. 



•* La Valette St. George, "fiber die Genese der SamenkOi'per," Arch.f. Mikr. 

 Anat., vol. i., 18G5. 



