No. 402.] THE ADVANCE OF BIOLOGY IN 1897. 491 
be tied so as to divide the free surface of the stump, two 
appendages will arise. A lesion of the humerus may provoke 
the development of an extra limb. 
Regeneration. — It was shown by Miss Peebles that in 
Hydra there are slight differences in the regenerative capacity 
of the different parts of the body, since the foot regenerates 
less well than the lateral parts of the trunk; also that 51, 
of a Hydra will regenerate. Morgan enumerated certain laws 
of regeneration of the earthworm. The parallelism of regen- 
eration and ontogeny was still debated. The truth that the 
essence of regeneration is not the restoration of some lost 
part, but the reassumption of the specific form, was illustrated 
by the regeneration of a jellyfish and a hydroid. 
Grafting. — As the results of Born and Jæœst marked re- 
spectively the years 1895 and 1896, so those of Crampton on 
the pupz of Lepidoptera marked 1897. In Lepidoptera, as in 
tadpoles and earthworms, the grafted pieces, even if belonging 
to distinct species, exert no mutual effect. In plant grafting, 
however, Daniel got a reciprocal effect. 
Sex. — No important advance in this subject was made in 
1897. Nussbaum, working on rotifers, got in some cases, as 
Maupas did, a predominance of females. This was due, Nuss- 
baum thinks, to an excess of food rather than a low tempera- 
ture, as Maupas concluded. 
Polymorphism and Metamorphosis, — The most interesting 
result was the rearing of an Amblystoma to the adult stages 
with retention of gills, by means of good food and a high 
temperature. 
Correlation. — False correlation was studied and measured 
by Pearson and discussed by Galton. Warren determined 
quantitatively the correlation between the various parts of the 
human skeleton. 
General Morphology and Physiology. — Contributions were 
made opposing the old interpretation of the germ layers. The 
Science of general physiology was becoming outlined with the 
aid of new text-books. The importance of ions in physiology 
received new and stronger confirmation; the correlation be- 
tween the composition of milk and the rate of infantile develop- 
