606 CHRISTIAN GCHAMPY AND H. M. CARLETON 
canaliculi or incisions seem to be incompatible with mitosis, 
direct division may occur in cells—other than those enumerated 
above—which contain such structures. Thus, amitosis has 
been observed in nuclei of the cells of the Wolffian ducts and 
germinal epithelium and Sertoli cells; also possibly in the 
gastric mucosa of some animals. 
The behaviour of smooth muscle when cultured in plasma 
confirms this idea. It has been shown (Champy, 5) that the 
nuclei of this tissue, when removed from the inhibitory influ- 
ences of the organism, multiply actively. At first they do so 
amitotically, and only when the typical structure of these 
nuclei has disappeared by a progressive ‘ de-differentiation ’ 
do they multiply by mitosis. Cultures of ovarian germinal 
epithelium behave in a similar manner. Again, the fundus 
glands of the human uterine mucosa have nuclei without 
incisions, while the cervical glands possess them. The former 
divide mitotically, the latter amitotically. And further, even 
in Adenomata (i.e. benign tumours) derived from the cervical 
glands does direct division persist. Only when such growths 
become carcinomatous do mitoses appear. 
We would here point out that incisions or lobulations of 
nuclei have only too often been mistaken as evidence of direct 
division. In our experience such appearances are only of value 
when an actual increase of the number of nuclei can be 
established. 
In conclusion, then, there is evidence that well-developed 
intranuclear canaliculi and incisions are incompatible with 
mitosis, a fact which possibly explains the tendency towards 
direct division in certain cells with specialized nuclei. 
12. SUMMARY. 
Variations in the shape of the nucleus have been described 
in different animal cells. In addition, the following factors 
have been shown to be responsible for nuclear shape : 
(1) Surface tension: when this is equal over the surface 
of the nuclear membrane, the nucleus tends towards the spheri- 
cal condition. When surface tension varies over the interface 
