ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 
17 
worthy of special attention. The author has some reason for believing 
that the difference may be due to the presence or absence of the breeding 
season in monkeys, and to periods in the human female which are in the 
one case favourable and in the other case not favourable to conception. 
If this be true the period of the human female which is unfavourable to 
conception would be comparable to the non-breeding season of monkeys, 
and the period favourable to conception with the breeding season of 
monkeys. It is not of course maintained that amongst civilised peoples 
at the present day there are definite breeding and non-breeding times. 
The comparison is in harmony with the view that at one period of its 
existence the human species had a special breeding season. 
Amitotic Nuclear Division in the Egg of the Hedgehog.*— Mr. 
Matts Modems gives a report of some observations on the ovary of the 
hedgehog, which appear to indicate the presence of an amitotic process 
of nuclear division in the germinal vesicle. Only a few instances of this 
process have been observed, especially in Vertebrates, and, as for Mam- 
mals, there is no other indication than that of Flemming, and the egg 
with which that observer had to deal was not normal. Under these circum- 
stances, the author believes that his case presents some interest, although 
no general conclusions can be drawn from it. It is perhaps merely 
abnormal, and we will content ourselves with directing our readers’ 
attention to the paper. 
Oogenesis in the Mouse.f — Dr. J. Lange finds that two phases of 
oogenesis and follicle-formation must be distinguished in the mouse. 
The first is embryonic, the second begins after birth, and continues for 
a prolonged period. (1) A large number of germinal cells in the 
embryonic ovary form primitive ova ( Ureier ). At the time of birth the 
undifferentiated germinal cells form a membrana granulosa around the 
primitive ova. Thus arise primordial follicles. At an age of about 
four weeks complete follicles are found, but of these a large number 
atrophy. (2) At an age of 6-8 weeks a new proliferating phase sets in. 
Individual cells of the germinal epithelium differentiate into primitive 
ova; along with the adjacent indifferent germinal epithelial cells these 
are sunk into the stroma, and form primordial follicles. The formation 
of fresh follicles continues to an advanced stage in the life of the mouse. 
Division of Ovarian Qva4 — Prof. J. Janosik has made some remark- 
able observations on the ovarian ova of various Mammals, guinea-pig, 
rabbit, &c. The ovarian ovum may form, especially in young animals, 
regular polar bodies, or precisely similar bodies. Thereafter, without 
any fertilisation, it may divide into nucleated segments either equal or 
unequal. Besides these actual divisions, there are often fragmentations*, 
especially in older animals. As division goes on, the membrana pellu- 
cida is lost, as in normal development after fertilisation. 
Embryonic Variations and Growth. § — Dr. A. Fischel has studied 
the variability and growth of duck-embryos. Individual variations in 
length occur at all stages, and affect both the whole and its parts. An 
* Bill. K. Svenska Vet. Acad. Handlgr., xxi. iv. No 2 (1S95) 12 pp. and 1 pk 
f Verb. Phys. Med. Ge3. Wurzburg, xxx. (189(5) pp. 55-76 (1 pi.). 
X Arch. f. Mikr. Anat., xlviii. (1896) pp. 169-81 (1 pi.). 
§ Morph. Jahrb., xxiv. (1896) pp. 369-401 (1 pi. and 10 figs.). 
1897 
c 
