84 THOMPSON YATES AND JOHNSTON LABORATORIES REPORT 
tron and staining of the cell be exceptionally good. These processes seem to 
correspond to the rudimentary tails originally described by us* 
m relation to the daughter elements of the first maiotic division in elasmo- 
branch fishes, and subsequently encountered elsewhere in corresponding cells 
by Meves and others. They are in all cases undoubtedly equivalent to the 
tail of the Spermatozoa and their appearance in the heterotype prophase of 
mammalia is distinctly interesting. 
While the above changes affecting the centrosomes are in progress other 
phenomena of a no less important character make their appearance in the 
archoplasm itself. During the migration of the centrosomes and after, it is 
seen that within the substance of the archoplasm small clear vesicles appear. 
They are of minute size, and often in considerable numbers. In each vesicle 
there is usually to be seen a small dark spot, and the archoplasm presents the 
appearance represented in (Fig. 21). 
Thus, so far as the attraction sphere is concerned, it may be said that 
the onset of the first maiotic division is marked by a peculiar migration of 
ihe centrosomes ; the development of rudimentary flagellae in connection 
with these bodies ; and the appearance of archoplasmic vesicles. 
When the first maiotic division is drawing to a close, and the cells 
assume the hour-glass appearance represented in (Fig. 26), the subsequent 
separation of the daughter elements is marked by the formation of an 
intervening spindle remnant, which for a time exists as a bridge between the 
cells. In the centre of this structure there are to be seen one or more stained 
particles, which have the appearance of thickenings on the original spindle 
fibres, and correspond to Fleming's intermediate bodies. In all other respects 
the reconstruction of the daughter cells and the recession of the active nuclei 
into rest corresponds to what has been described in the case of the pre-maiotic 
divisions. 
THE SECOND MAIOTIC (HOMOTYPE) DIVISION. 
The daughter elements of the first maiotic division are represented in their 
resting condition in (Fig. 27). In all stages after their formation the archo- 
plasm is large, while it seems doubtful in many instances if the centrosomes 
ever come to lie in the archoplasmic mass. At all events, these bodies in a 
very early stage are visibly detached from the rest of the sphere, and 
consequently it is obvious that in this generation there exists the same 
dismemberment of the constituents of the attraction sphere which marked the 
onset of the maiotic change. Besides the extra-archoplasmic position of the 
centrosomes the archoplasm itself becomes again filled with clear vesicles 
(Figs. 27, 28) ; while there exists as well the conspicuous irregular chromatic 
body in the cytoplasm (Fig. 28). 
Thus, in this generation, all the peculiar cytoplasmic features which were 
assumed at the beginning of the maiotic change are again in evidence. 
The cells produced by the heterotype division remain in a resting condition 
a relatively short time, and the onset of the second maiotic (homotype) division 
is ushered in, so far as the nucleus is concerned, by the formation of chromatic 
* Moore. On the Spermalogenisis in Elasmobranchs. Quart. Journ. Micro. Sci., 1906. 
