No. 387.] REVIEWS OF RECENT LITERATURE. 257 
and also the theory that accounts for maturation on the ground that 
it is getting rid of the male element of an originally hermaphrodite 
egg nucleus. 
4. All theories must be rejected which consider fecundation as 
the furnishing by the male of the number of chromosomes subtracted 
by the polar globules. The loss of one-half of the chromatic matter 
does not, of itself, prevent the egg from developing, for the half 
number of paternal chromosomes can make the egg develop. 
s. The sexual attraction is not located in the nucleus. 
6. Two things must be distinguished in fecundation: (a) the com- 
munication to the egg of a vital energy which permits it to segment 
and to develop; (4) the communication to the product of the advan- 
tages resulting from amphimixia and the possession of the paternal 
hereditary characters. As for the second point, my experiment fur- 
nishes no indication; as for the first, it shows that the theories of 
fecundation reconcilable with it are those which present the phenom- 
enon as the conveyance by the male of a special energetic plasm 
(Kinoplasma) contained perhaps in the spermocenter. 
7. There is in the ovular cytoplasm no fixed specific architecture 
whose conservation is a condition of development; if a structure 
exists, it is conditioned by the mutual reactions of parts and can 
reéstablish itself as often as it is altered. 
8. The celebrated experiment of Boveri, so strongly contested, 
especially by Seeliger, is demonstrated, if not true, at least possible ; 
the gravest objection that has been made to it (the impossibility of 
the development of an ovular cytoplasm without nucleus) being 
experimentally suppressed. 
Temperature and Rate of Regeneration. — It has long been 
known that in every organism there is an optimum temperature for 
growth above and below which growth occurs more slowly. That 
the same is true of regeneration has been shown by the recent work 
of Lillie and Knowlton on Planaria torva. Miss Peebles has done 
similar work on Hydra grisea and H. viridis. At 18-24° C., of H. 
grisea there regenerated in 2 days 0% ; 3 days, 26% ; 4 days, 95%; 
of H. viridis, 2 days, 38% ; 3 days, 100%. At 26-32° of H. grisea 
there regenerated in 2 days, 75%; 3 ene 100% ; of H. viridis in 2 
days, 98.5% ; 3 days, 100%. At 12° C. there regenerated of Hydra 
viridis in 4 days, 13%; 5 days, 24%; 6 days, 71%; 7 days, 100%. 
1 Peebles, Florence. The Effect of Temperature on the Regeneration of 
Hydra, Zool. Buil., vol. ii, pp. 125-128. 
