GROWTH-CHANGES IN MAMMARY APPARATUS OF DASYURUS. 211 
in Nos. 15 and 16, that is to say, in animals with embryos in 
a late blastocyst stage or just attached to the uterus. 
The whole of this growth is brought about by the mitotic 
divisions of the original epithelium lining the first tubules, 
and throughout the sections, more especially in those of 
No. 28, mitotic figures are to be found in the growing portions 
of the gland (fig. 14). 
There remain now two animals. Nos. 29 and 30, which were 
killed at a much longer time after ovulation. The record of 
the first of these has already been given. In the second the 
record is not so complete, but it would appear from the 
sections of the mammary glands that the growth of these 
latter had been carried on to a somewhat later stage. The 
animal was killed nineteen days after the final copulation. 
The sebaceous and sweat-glands in No. 29 show a state of 
development comparable in all respects with that in animals 
after parturition, and the pouch was tumid, lax and moist. 
The mammary gland, too, is also in a condition resembling 
that found in the stages twenty-four hours and thirty-six 
hours after the birth of the young. The alveoli are fully 
formed with their walls one cell thick, and their cells are in 
a state of slight secretory activity. In the alveoli, the 
tubules, and the ducts leading into the main ducts is to be 
found a secretion which looks much more like milk than 
colostrum, and is in all probability the former, although there 
is no record that it was expressible from the teat of the 
living animal. 
In No. 30 the sebaceous and sweat-glands resemble those 
of No. 29, but the mammary gland is in a more advanced 
condition. The general appearance is somewhat in advance 
of that of the stage thirty-six hours after birth-, for the 
alveoli are more distended, and the ducts more enlarged. 
Again we have the appearance of a secretion which is almost 
certainly milk, and the cells of the single-layered epithelium 
lining the alveoli are in a state of moderate activity. 
Examination of a section of this gland (fig. 10) shows 
that it is in a more advanced state than the glands of animals 
