210 
CHAS. H. O’DONOGHUE. 
embryos in the late blastocyst stage. The glands remain 
constant in size in the rest of the animals in this series. 
The sweat-glands also undergo hypertrophy, and continue 
throughout in a state of moderate activity, just as they do in 
the pregnant animals. This activity results in the production 
of the secretion which causes the inside of the pouch to 
become moist. 
The Mammary GTands. 
Again we find that the mammary gland itself is the seat of 
the most marked growth during the period after ovulation in 
these non-pregnant animals. In No. 26, which had twenty- 
three unfertilised eggs in the uteri, the gland has in addition 
to the ordinary tubules of the resting gland, a large number 
of solid bud-like out-growths. These projections give the 
gland, when viewed in transverse section, a far more compact 
appearance than it has in the resting condition, and at the 
end of the growth period they become transformed into 
secretory acini. 
In the next two examples, Nos. 27 and 28, the ovaries 
contain well-marked corpora lutea, which are fully formed 
and about full-grown. The mammary gland is still further 
enlarged, and composed in its deeper parts of a mass of 
alveoli, the walls in most of which are lined with a double 
layer of cells, of which the outer layer has become much 
flattened. But in a number of cases fully formed acini with 
a single-layered epithelium are present. The tubules .near 
the main ducts are dilated, and both are full of a secretion 
that is similar in appearance to colostrum, and was, in one 
case at any rate (No. 28), expressible as lymph from the test 
of the living animal. The full extent of this enlargement 
may be realised by a comparison of fig. 9, which is from 
a section in series No. 27 with fig. 2, from a section 
of the resting gland. In series No. 28 the gland is in a still 
more advanced condition, but the tissue itself has not been 
so well preserved. The stage of development reached by 
these two would appear to correspond most nearly to that 
