210 DR. F. WOOD-JONES ON THE 
seventy or eighty years when the sections were cut, and yet the 
histological condition of the tissues remains extremely good. 
The nestlings are immature and pink, and are devoid of obvious 
hair except along the margins of the tail. The eye has become 
further reduced from the late feetal condition; the ear appears 
in extraordinary proximity to the shoulder, and the genitalia are 
in practically their adult condition. The vertex-rump measure- 
ment of.one (2) is 59 mm. (text-fig. 3, A) and of the other (¢) 
62 mm. 
The serial sections of the female specimen show that a great 
adyance has been made on the condition seen in the full-term 
embryo, the development of the genital system taking place 
between the 33 mm. and 59 mm. stages being remarkable. 
In the first place the utero-vaginal canal has lost all trace of 
its bilateral origin, for the Mullerian tract is now a wide canal 
with well differentiated walls. The whole picture of the pelvic 
relations has altered by this rapid growth of the female genital 
passages, for whereas in the embryonic stages the urinary tract 
was far wider than the genital passage, in the nestling the utero- 
vaginal canal is the most conspicuous viscus in this region 
(BIR esos. 2): 
Another well-marked change is the complete separation of 
the cavities and the almost complete separation of the walls of 
these two passages, for it is only over a very small area that the 
musculature of the genital and urinary tracts becomes united. 
But although the separation of the two channels has thus become 
more marked, there is as yet but little advance on the embryonic 
condition towards the establishment of a new orifice for the 
female ducts. The epithelial ingrowth at the base of the genital 
tubercle has become more conspicuous, and with the increased 
growth of the parts it is still further separated from the 
centrally-lying urethra. 
Advanced as is the development of the female passages at this 
stage, there is, however, still a very imperfect union of the 
epithelial ingrowth and the utero-vaginal canal. 
In the specimen examined in serial sections it is only upon 
the right side that the ingrowth meets the patent utero-vaginal 
canal; so that it is only on the right of the urinary passage that 
there is even an epithelial continuity between the female genital 
system and the surface of the body. The left side of the epithelial 
crescent is well developed, but it remains widely separated from 
the utero-vaginal lumen (PI. ITI. fig. 2: the figure is reversed). 
(ii.) The Adult. 
There is no need to describe the uterus and its adnexa in the 
adult, for this description has been furnished many times by 
comparative anatomists who have examined second year females. 
It was evidently only the female of the second year that was 
examined by John Hunter, for he says (11):—‘‘ There is no 
common vagina; the vagina is very long and runs in a serpentine 
