8d THOMPSON YATES AND JOHNSTON LABORATORIES REPORT 
The nucleoli of such pre-maiotic cells become altered in appearance 
during division, sometimes breaking up into fragments, which disappear in 
the cytoplasm. In other instances they persist, and are visible in one or 
both of the daughter cells for a considerable time. After the daughter cells 
separate, the nuclei gradually pass back again by insensible degrees into the 
condition of complete repose originally possessed by the parent form. (Fig. 
8 and 9.) 
Such, then, is the character of the pre-maiotic cell division of mammalia. 
It is a process by which the permanent cell constituents, nucleus, sphere, and 
cytoplasm, ar? accurately halved, and their sundered moieties eventually re- 
constructed into two similar elements in the place of one. Substantively 
each daughter cell is a miniature of the original parent, and the process of 
division may go on rapidly, as during segmentation, so that the ultimate 
products are highly reduced images of the original egg ; or as during the later 
growth of the embryo and during the replacement of tissue in the adult 
body, each daughter of division may grow again to its original size before a 
subsequent mitosis. 
OUTLINE OF THE DEVELOPMENT OF THE MALE SEXUAL CELLS. 
In the male sexual glands of mammals before the maiotic process inter- 
venes, and throughout the rest of the body, except in those abnormal cases 
where malignant growths are superimposed upon the ordinary course of 
development, the elements which fill up the testicular tubules have been pro- 
duced from the original blastomeres by repeated divisions of the above within 
maiotic type. During the first onset of the maiotic change cells lying within 
the mass filling up the tubules pass into the maiotic condition, and these are 
eventually discharged as Spermatozoa. The tubules, when mature, be- 
come converted into hollow pipes of connective tissue, lined inside with a 
single layer of pre-maiotic elements. These latter, by continuous divisions, 
give off internally layer after layer of cells that pass immediately through the 
maiotic change, eventually become shed into the lumen of the tubule as 
mature spermatozoa. 
In an adult tubule there are, however, besides the layer of pre-maiotic 
sperm-producing elements, cells which are of a different character. These 
are the so-called foot cells, and although their origin is by no means as clear 
as it might be, their function is undoubtedly connected with the maintenance 
of future crops of Spermatozoa. 
In the adult mammalian tubule the cells of the pre-maiotic layer have 
ill-defined walls, and 111 some instances it is suggested that the whole of this 
layer consists in reality of a nuclear syncitium rather than a pavement of 
individual cells. Moreover, in portions of this layer there exist nuclear 
figures, which certainly suggest amitotic budding. That is to say, appear- 
ances which would seem to indicate that at certain times the cells of the pre- 
maiotic layer are multiplied by amitosis before passing on into the later 
stages. The suggestion of amitosis in the pre-maiotic layer in mammals is 
of great interest from a theoretical point of view, and it is in conformity 
with appearances observed during the study of the periodical maturation 
