No. 383.] THE ADVANCE OF BIOLOGY IN 1896. 871 
than the normal ones. In the case of Crustacea the normal 
form of the organ may reappear after several molts (Przibram). 
A very extended study on regenerations in earthworms was 
made by Heschler. 
Grafting. — This year afforded the marvelously successful 
results of Joest in grafting earthworms, not only one part of 
the worm being united to another part, but one individual to 
another. 
Sex and Secondary Sexual Characters. — New experiments 
on sex control confirmed, on the whole, the idea that femaleness 
results from rich nutrition. Marchal showed that neuter wasps, 
when through the death or sterility of the queen there are no 
young in the nests, feed on the larval food and become fertile 
females. 
Polymorphism, Metamorphosis, and Alternation of Generations. 
—Some advance was made this year in answering the question, 
Is polymorphism blastogenic or somatogenic? What rôle do 
the intrinsic conditions of the individual play, and what environ- 
ment? No doubt there must be a substratum capable of 
responding in two or more ways, but which response shall be 
called into action, and how far it shall go, these are determined 
by extrinsic factors. The theory that a double habit (e.g., the 
habit of a gall insect in stinging two kinds of trees) may lead 
to polymorphism was advanced by Beijerinck. 
Correlation. — The most important contribution of the year 
was that which Pearson made to the mathematical study of the 
subject. Several authors contributed exact data on correlation 
in various species. Many special cases of correlation were 
described. 
General Morphology and Physiology.— The discussion over 
the significance of the cell as a unit in the body was continued 
in France by Delage and Le Dantec. The idea that metameres 
are, phylogenetically, secondary divisions of the trunk gained 
ground. 
One of the most important works of the year in general 
physiology was that of Loew, on the Energy of Living Protoplasm, 
in which the chemical explanation dominated. Progress was 
made towards a clearer understanding of the way in which sun- 
