THE MAIOTIC PROCESS IN MAMMALIA 
8 
occurring in amphibia.* We would, however, at present go no farther in 
this matter, as the work upon amphibia is incomplete. 
In the adult mammalian tubule we have then a hollow pipe, lined inside 
with a layer of pre-maiotic sperm cells, and between these are inter- 
spersed a number of foot cells, represented red and grey respectively in 
figures on Plate VII. On the inner side of this layer there always exist 
numbers of older elements, which in the figure have been left un- 
coloured, and will be dealt with later. In such a tubule it will be found 
that at certain points individual cells, and patches of cells belonging to the 
pre-maiotic layer, are undergoing mitosis, and that this division is always of 
the pre-maiotic type. Moreover it can often be seen that at each such divi- 
sion of the pre-maiotic elements one of the daughter cells passes somewhat 
inwards towards the interior of the tubule, and then enters immediately upon 
the maiotic stage (Fig. 55). Not infrequently cells belonging to this series 
are seen which contain one, two, or even four nuclei, and it seems 
probable that the syncytial mass of cytoplasm has not divided up along with 
the nuclei : multi-nucleate masses being the result. This inner layer of nuclei 
coloured blue (Figs. 55 and 56) grow at first slowly in size relatively to the 
elements in the pre-maiotic layer. Subsequently, however, they grow much 
more rapidly, and at the same time they assume a distinctly chromatic and 
granular appearance ; this change in reality marking the onset of the maiotic 
transformation. Such cells are, as a matter of fact, entering upon the long 
prophase of the first maiotic heterotype division (Fig. 56). When these cells 
have obtained the dimensions represented in (Fig. 56) they divide and give 
rise to daughter elements lying in the position represented in (Fig. 57). Sub- 
sequently the latter elements again divide, producing th second maiotic 
(homotype) division. These last products occupy the position represented in 
(Fig. 58), and without further division are transmuted into groups of sper- 
matozoa, their connection with the foot cells becoming at the same time 
.obvious (Fig. 58). 
Such then is a brief outline of the stages in the maiotic transformation 
as it occurs in the adult mammalian tubule during Spermatogenesis, and it 
remains for us now to consider in detail the various maiotic phases. 
THE FIRST MAIOTIC (HETEROTYPE) DIVISION. 
The nuclei which are about to enter upon the prophase of the first maiotic 
division become finally granular and chromatic, and after at first containing 
one or two large nucleoli t are seen to possess several scattered about the in- 
terior of the nucleus. Towards these chromatic centres the chromatic reticu- 
lum is curiously centred, as in Fig. 10. 
In mammals theappearance and arrangement of these chromatin centres 
is highly remarkable and interesting. They correspond to the structure which 
in 1904 we called the " chromosome anlagen," visible in the rest, and pro- 
phase of the pre-maiotic cells of Periplaneta. They are also similar to the 
bodies (" Pro-chomosomes) subsequently described in the first maiotic pro- 
phase by Strasburger, Miyaki, and Overton in a number of plants. 
* These observations are contained in a paper not yet published by Miss Embletqn. The material was, 
however, worked out in the laboratories of. the Cancer. Research, Liverpool University. 
t Farmer and Moore, on the maiotic phase (Reduction divinus) in Animals and Plants. Quart. Journ. 
Micro. Set., Vol. 48. 
J. See Strasburger, Miyaki, and Overton. 
