EMBRYOLOGICAL, REPRODUCTION, SEX, ETC. Gen. Sub. 55 
First differentiation of body-cells and germ-cells in sponges ; Maas 
(322). 
Comparison of the development of the egg in oviparous and viviparous 
Aphides ; Lemoine (301). 
On embryonic membranes ; Semon (507). 
Formation of germinal layers ; Will (577). 
Rate of growth : In mice, greatest immediately after birth, decreases 
for 18 days, then increases for 3-4 days ; Saint-Loup (482). 
Growth of Balanoglossus larva : First a period of great increase in size, 
cells increasing in numbers; second, a period of decrease in size, in which 
no new organs are formed ; third, the body begins again to enlarge, the 
increase in size takes place in all the organs at the same time, aud not 
as in the early stage, at the expense of one set of structures alone ; the 
increase in length is due not to apical growth, but to general interstitial 
growth ; Morgan (376). 
Experiments on Heteromorphosis ; Loeb (316), Bickford (40). 
8. Reproduction, Sex, and Heredity. 
a. Reproduction and Sex. 
Determination of sex in relation to fertilisation ; Gasco (178). 
Conjugation of nuclei in an adult tissue : intestinal epithelium in Tor- 
cellio ; Ryder & Pennington (477). 
Plastogamy of Actinosphcerium : No associated mitosis ; no subsequent 
encystment ; probably it mitigates the intimacy of the amphimixis, 
which probably occurs at time of encystment. After many divisions the 
individuals were too small to capture their food; the only possible 
escape from starvation was coalescence ; Johnson (261). 
Asexual reproduction in Turbellarians. Paratomy or division accom- 
panied by the formation of organs : — 
(а) Paratomy with regeneration of complete parts of the body. 
(1) With deferred formation of organs. 
(2) With simultaneous formation of organs. 
(б) Paratomy without regeneration of complete parts of the body. 
(3) With precocious formation of organs and resorption. 
(4) With precocious formation of organs, but no resorption. 
Keller (265). 
Asexual reproduction of Turbellarians : In Stenostoma , regeneration of 
brain, “ eye,” pharynx, &c., from Stammzellen, i.e ., unbranched connec- 
tive tissue cells. Their function is (1) to accomplish regeneration and 
fissiparous proliferation, and (2) to form the reproductive organs. 
Organogenesis during asexual reproduction is quite the same as in the 
development of the embryo ; Keller (266). 
