22 J. E. WODSEDALEK. 



centrosome together with the mass of cytoplasm has not hereto- 

 fore been, to my knowledge, recorded. The body usually stains 

 as deeply as it does in the earlier stages for some time after the 

 comparatively large mass of cytoplasm containing it is completely 

 separated from the rest of the cell or young spermatozoan. 



In general, the behavior of the centrosomes in the development 

 of the spermatozoan of the pig does not differ greatly from the 

 conditions found in some of the other vertebrates. However, it 

 might be well to briefly point out some of the differences. In the 

 spermatids of the salamander, according to Meves ('97), the two 

 centrosomes lie quite at the periphery of the cell and from the 

 outer one grows out the axial filament. The two centrosomes 

 leaving the idiozome by which they are first surrounded, now 

 pass inwards toward the nucleus, the outer one meanwhile 

 becoming transformed into a ring while the axial filament 

 passes through it to become attached to the inner centrosome. 

 The latter pushes into the base of the nucleus and enlarges 

 enormously to form a cylindrical body comprising the main 

 portion of the middle-piece. The ring divides into two parts, 

 the anterior of which gives rise to a small body at the posterior 

 end of the middle-piece identical with the end-knob. The other 

 part of the ring wanders out along the tail and finally lies at the 

 limit between the main part of the latter and the end-piece. 



In the pigeon, according to Guyer ('oo), the centrosome divides 

 and moves out of the sphere and further away from the nucleus. 

 The two new centrosomes move apart, but remain connected 

 by a mass of material which later disappears and a very delicate 

 fibril uniting the two centrosomes exists in its place. One of 

 the centrosomes enlarges and transforms into a complete ring. 

 The connecting fibril can later be seen passing from the smaller 

 centrosome back through the ring and outside the cell. The 

 centrosomes next approach the nucleus and as they draw near a 

 slight invagination appears in the nuclear wall and the small 

 centrosome moves into it. 



In the mammals, the work of Lenhossek on the rat ('98) and 

 Meves on the rat, guinea-pig and man ('98, '99) gives a result 

 similar to the condition found in the salamander. In all these 

 mammals the young spermatids contain two peripherally placed 



