4o6 NATURAL SCIENCE. June. 



account of excretion and of the relations between secretion, excretion, 

 and the formation of inter- and extra-cellular matrices is excellent. 

 The second section of this chapter describes the phenomena of change 

 of form, which Verworn, following Haeckel, regards as divisible into 

 two separate, but mutually dependent, groups, the phylogenetic and 

 ontogenetic series of changes. In these, heredity is the conservative 

 force ; adaptation, the changing factor. In a short discussion of 

 heredity, he points out that Weismann has practically disproved the 

 inheritance of acquired injuries, but that in our ignorance of the 

 correlations between organs it would be almost impossible to prove 

 the definite inheritance of acquired characters. Moreover, he would 

 not expect that experiments, unless conducted through a very large 

 series of generations, could be expected to give any definite results. 

 In a similar short discussion of adaptation he points out the direct 

 effect of environment in shaping an individual organism, and the 

 effect of natural selection in changing the form in a phylogeny. 

 Obviously, there was no space for a full treatment of problems so 

 vast as heredity and adaptation, but the mere raising of them in 

 appropriate places in the development of the subject is an enormous 

 gain to the philosophical treatment. 



Then follows a general discussion of ontogenetic change, of 

 growth and reproduction, of cell-division, fertilisation, of ontogenetic 

 changes in single-celled creatures, and of the general phenomena of 

 ontogeny in Metazoa. Verworn does not attempt a condensed 

 account of embryology, but merely specifies the general nature of the 

 changes that take place, summing them up in the sentence : " Cell- 

 division, equal and unequal, and coherence of the results of division, 

 are the factors that determine the embryonic development of a 

 specialised cell-community." It is perhaps to be regretted that no 

 room was found for a discussion of modern criticisms of the cell- 

 theory : there are, at least, suggestive parallels to be drawn between 

 the uni-cellular development of, say, a Vovticella from a spore, and the 

 shaping and m.oulding of a metazoon. 



The last section of this chapter refers to what may be called the 

 vital transformations of energy in living organisms. The author 

 discusses in detail the activities of living creatures, their movements 

 of all kinds, and their productions of light, heat, and electricity. To 

 the physiologist, accustomed only to consideration of ciliary motion, 

 protoplasmic motion, and muscular motion, the comprehensiveness of 

 this section will come very pleasantly. 



The fourth chapter, 60 pages, on the general conditions of life, 

 seems to us the most attractive section of the whole volume. After a 

 brief review of the positive and negative conditions of life, the author 

 passes to a historical and critical treatment of theories of life and 

 death, and of the definite facts upon which theories must be based. 

 His discussion of ancient and modern theories of the origin of life and 

 of known facts leads him to the plain conclusion that what we call 



