GROWTH-CHANGES IN MAMMARY APPARATUS OF DASYURUS. 199 
during this period. In the tubules of the deeper part of the 
gland are to be found a few structures of doubtful signifi- 
cance, which may or may not represent mitotic figures, but 
the actual formative growth of the gland does not appear to 
start until after ovulation. 
Changes during Pregnancy. 
The Pouch. 
It would appear from Professor Hill’s notes that the 
changes which occur in the pouch during pregnancy are 
very well marked, and give some indication of the stage of 
development reached by the embryo in the uterus. In the 
resting animal the pouch is a small circular depression about 
10 mm. in diameter and 5 mm. in depth, and it is dry inside. 
In the period proceeding ovulation its lips become slightly 
tumid and the interior slightly moist, but after ovulation and 
fertilisation the changes become much more apparent. The 
pouch slowly enlarges and loses its circular form, becoming 
somewhat elongated in an antero-posterior direction. Its 
margins swell and become tumid, and the interior becomes 
more moist. During the life of the animal the pouch, of 
course, becomes very dirty, and so needs to be cleaned before 
receiving the newly-born young. As soon as the secretion 
of the cutaueous glands appears in some quantity within the 
pouch, the mother commences to clean it out, at first cen- 
trally, and then outwards towards the margin, until at last 
the whole interior is quite clean. This cleaning process 
usually appears to take place during the time while the 
embryos are in the blastocyst stage. After this, the enlarge- 
ment still goes on, so also does the production of the 
secretion of the cutaueous glands, which can sometimes be 
seen as drops of a reddish fluid in the pouch. The pouch 
itself becomes lax and flaccid, and on its floor the sebaceous 
glands begin to show beneath the skin. Towards the end of 
pregnancy these glands are very large and prominent, the 
