No. 402.] THE ADVANCE OF BIOLOGY IN 1897. 493 
evolution. Many workers pleaded for an explanation of adapta- 
tion on the basis of self-adjustment. No real progress was 
being made in this field, because the method was bad. 
Geographic Distribution. — There was especial activity in 
the study of marine and fresh-water plankton and the theory 
of bipolarity in the distribution of faunas. Of general works 
may be cited Lydekker on mammals in general and Sclater on 
marine mammals. 
Mental Functions. — The review of the literature in this 
department occupies one-fifth of the book. The work is too 
voluminous and technical to be summarized here. 
General Theories. — Very little. A duel between Hertwig 
and Roux over the word * Entwickelungsmechanik." A sug- 
gestive work by Pearson on “ The Chances of Death.” 
General biology has this year made its greatest advances in 
the study of variation, grafting, in general physiological prob- 
lems, and in the chemistry of vital phenomena. 
