THE MAIOTIC PROCESS IN MAMMALIA 
condensations, which foreshadow the chromosomes of the subsequent mitosis. 
These, in the guinea pig, are sixteen in number. No true spirem appears to 
be formed, and the best description of the process is to say that the chromatic 
granules become at first aggregated in clouds, and after a time into two rows 
in each. In this way the young chromosomes have the appearance of being 
longitudinally split (Figs. 27, 28). 
At the same time the centrosomes, usually quite near the periphery of the 
£ell, migrate from one another to opposite ends of the cytoplasm. Radiations 
appear, the nuclear membrane vanishes, and the sixteen chromosomes become 
attached to the spindle as in an ordinary pre-maiotic division. The individual 
halves of each separating to form the daughter nuclei in a similar manner. 
We have not hitherto been able to observe the formation of abortive 
flagellae in these cells, as in the corresponding generation of elasmobranchs. 
At the close of the second maiotic division the archoplasm, together with 
its vesicles, disappears, as it does in the preceding generation, and the 
spindle fibres form in a marked manner once more the bridging structure 
between the daughter cells represented in fig. 
THE SPERMATIDS. 
The reconstruction of the cells produced by the second maiotic (homo- 
type) division, which form the final spermatids, is similar to that witnessed in 
the preceding generation. The centrosomes appear to be dissociated from 
the archoplasm, and a gradual metamorphosis is inaugurated which ter- 
minates in the formation of the mature spermatozoa. 
In the present paper it is intended to confine the description of the events 
which lead up to the production of the mature male element to its earlier 
phases. In the first place, it is such phases only which appear to be of wide 
significance. Secondly, our account of these changes will be found in details 
not to agree completely with the work of Meves ; but the differences are not of 
sufficient magnitude to require special treatment ; whilst thirdly, in the work 
above referred to, the latter parts of the transformation have been so 
admirably illustrated and followed that any fresh description of them here 
seems quite unnecessary. 
By the time the daughter elements produced by the second maiotic 
division have come to rest, the archoplasm is of conspicuous dimensions, and 
the centrosomes may be found in the cytoplasm, sometimes near the chromatic 
body, sometimes quite on the periphery of the cell (Fig. 32). At an early stage 
archoplasmic vesicles appear, and these structures rapidly grow to much 
greater prominence than in either of the two preceding generations (Fig. 35). 
At the same time that the vesicles enlarge they decrease in numbers, until 
one or two only are left in the archoplasm, as in (Figs. 38, 39, 40, 41 ). In all 
cases it appears that only one is finally left, and this grows rapidly, presenting 
a well-marked membrane, as in (Fig. 41). At the same time the central stain- 
ing mass in the vesicle becomes more pronounced, and from it there grows out 
a more faintly staining material, which we will call the intermediate substance 
(Fig. 42). About this time the archoplasmic vesicle (Plimmer's body), together 
with the remaining mass of the archoplasm (residual archoplasm) becomes 
