28 
SPERMATOGENESIS OP NORMAL 
TRANSFORMATION OF THE SPERMATID INTO THE ADULT 
SPERMATOZOON. 
i 
An adult spermatozoon as it exists in the vas deferens is 
shown in Fig. 27. The head is long and narrow and is intensely 
stained by nuclear dyes. Favorable preparations show faintly 
a spiral or vesicular arrangement of part of the chromatin m the 
interior. At the anterior end of the head is a slender fine- 
pointed head-spine. The head at its posterior end connects 
directly with the long cytoplasmic tail. No middle piece is 
visible. The tail and head-spine are, very difficult to observe 
accurately, and but little of the details of their structure could 
be worked out. The only satisfactory way to gain a knowledge 
of the spermatozoon at all, in fact, is through a study of its 
development. 
Ballowitz^ in his description of the spermatozoa of birds Is 
somewhat in error in regard to the spermatozoa of pigeons (cf. 
his drawing Fig. 91, Plate XVII.). He has seemingly mistaken 
the head for the tail. 
Before the spermatid begins its transformation, it is quies¬ 
cent for a considerable period of time if one may judge by the 
large number that is nearly always observable in any section. 
When once the change begins, it is probably completed in a 
relatively short time. The spermatid, in the resting condition 
after the last division, has a very characteristic appearance 
(Fig. 17). The nucleus is round and bears most of the chroma¬ 
tin at its center in the form of a large sphere which from optical 
section seems to be hollow. Fibers of linin radiate from 
the central mass to the nuclear membrane which is lined by a 
thin shell of chromatin. Not infrequently several small spheres 
of chromatin may persist at the center of the nucleus instead of 
one large one. The centrosome lies to one side of the nucleus 
imbedded usually in the sphere. The cell membrane is at times 
very indistinct. 
The first change to be observed is in the centrosome. It 
divides and moves out of the sphere and further away from the 
1. Ballowitz, E: Untersuchungen ueber die Struktur der Spermatozoon 
Arch. f. mikr. Anat., XXXII., 1888. 
