THE SPERMATOGENESIS OF DOMESTIC MAMMALS. 367 
perforatrium just as WODSEDALEK has shown to be the case in the pig (Figs. 
71—73). 
With the migration of the sphere the cell becomes elongated and 
the nucleus shifts its position near to the anterior end of the cell, while the 
cytoplasm collects at its posterior portion (Figs. 66—71). Most of the 
chromatic material now collects more and more near the periphery of the 
nucleus (Figs. 65—67), and the anterior centrosome comes so close to the 
nuclear wall as to be placed in a small depression which meanwhile appears 
a5 the posterior end of the same (Figs. 70, 71, 73). The bulk of the inner 
centrosome of the peripheral ones passes into the formation of the axial 
filament, and the centrosome as such finally disappears. The disc shaped or 
round posterior centrosome gradually increases in size and the axial filament 
extends backward, directly passing through it (Fig. 72). After the projection 
of the tail out of the cell, this posterior centrosome diminishes in size and 
moves apart from the anterior (Figs. 70, 71), until it becomes entirely lost 
to view (Figs. 73, 75). Whether this centrosome is thrown off together 
with a big mass of cytoplasm, during the final development of the sper- 
matozoa as is described by WopsEDALEK (13) in the pig, is in my prepara- 
tions not determined. 
The general behavior of the centrosomes in the development of the 
spermatozoa in the horse is similar to that in man and in the rabbit, as 
stated by Meves (1898). Finally the chromatoid corpuscles are > cast off 
together with a mass of cytoplasm, and the mitochondria develop to form 
the middle piece (Fig. 73). 
The ripe spermatozoa found free in the lumen of the tubule, appear to 
vary considerably in size. This, however, is owing to the fact that the head 
of a ripe spermatozoon is flattened, and so the lateral view gives quite a 
different impression to that of the flattened side (Figs. 74, 75). 
VII. Chromatoid Corpuscles. 
It is not possible to positively identify the chromatoid corpuscles until 
after the postsynapsis. But as stated above, ina stage immediately following 
the synapsis, small granules make their appearance in the cytoplasm closely 
