THE SPERMATOGENESIS OF DOMESDIC MAMMALS. 393 
amount of chromatin granules are characteristic of the nuclei of daughter 
cells which are produced by amitosis, while the nuclei of the spermatogonial 
cells are usually spherical and contain numerous chromatin granules. No 
case was observed where a cell divides mitotically which has once been 
divided by amitosis. 
The above data show conclusively that the cells divided by amitosis do 
not develop to sex cells, but probably degenerate and are used as nutritive 
materials by the germ cells as vom Ratu asserts, where he says: “ Faßt 
man nun in kurzem die Resultate meiner Untersuchungen bei Astacus. mit 
den von Platner und Hermann bei den Pulmonaten, der Maus und dem 
Salamander gewonnenen Beobachtungen zusammen, so glaube ich zu folgender 
Schlußfolgerung berechtigt zu sein: In allen Fällen, in welchen eine 
amitotische Kernteilung im Hoden beobachtet wird, vollzieht sich diese 
Kernteilung nur an den Randzellen (Stützzellen). Letztere stehen weder mit 
dar eigentlicken Spermatogenese noch mit den Regenerationserscheinungen in 
direkter Beziehung. Die Samenbildung kommt nur auf mitotischem Wege zu 
Siande und ebenso die Regeneration. Eine Umwandlung von Randzellen 
(Stutzzellen) zu Spermatogonien findet nicht statt. Demnach bildet die 
wnitotische Kernteilung im Hoden hinsichtlich ihrer biologischen Bedeutung 
keine Ausnahme mehr und steht einer einheitlichen Auffassung der amitotischen 
Kernteilung nicht mehr im Wege.” 
As many authors have already pointed out, it is more probable that 
nmitosis is the result of special nutrition by which the spermatogonial cells 
are affected. The following facts may be cited as favorable to this view: 
1. As stated above the nuclei of the spermatogonia which begin to divide 
amitotically, are always of large size. 2. Sometimes the prophase nuclei in 
which the spiremes are clearly seen, rapidly increase in size, becoming about 
twice as large as those of the spermatogonial cells, and finally come to be 
divided by amitosis. 3. In the testes of quite young animals amitosis occurs 
ınore frequently than mitosis. | 
Parrerson (’08) has found amitotic division in the pigeon’s egg and 
believed that amitosis is the result of special physiological conditions which 
create a stimulus to cell-division where he says: “Just what these conditions 
are, we are of course unable to say, but whatever factors are involved in 
