SOME NEW BOOKS. 



HERTWIG'S THEORY OF BIOGENESIS. 



Die Zelle und die Gewebe. Grundziige der allgeraeinen Anatomie und 

 Physiologie der Gewebe. Zweites Buch. By Prof. Dr. Oscar Hert- 

 wig. 8vo, pp. viii. + 314, with 89 illustrations. Jena: Gustav Fischer, 

 1898. Price 7 marks. 



Although this book comes at an opportune moment, Avhen the contro- 

 versial fires of the " evolutionists " and " epigenetics " are burning low, 

 and contains many interesting observations, it will not, in our opinion, 

 mark any great epoch in the history of the subject. Even the most deter- 

 mined opponent of the neo-evolutionistic school will probably admit that Weis- 

 mann's latest most important work, " The Germ-plasm," is, in some respects at 

 least, a work of genius ; but this could be hardly said of the present volume. 

 Indeed, after reading the three hundred odd pages it contains, we must 

 confess to a feeling of disappointment that Dr. Hertwig has not been able 

 to state a stronger case for himself and his colleagues. As a destructive 

 critic he is generally convincing when he attacks the " evolutionists," and 

 he has no doubt done valuable service in overthrowing much of what 

 was at one time freely accepted by many biologists as fact, which can 

 now be no longer upheld in the light of recent observation and experiment. 

 But we much doubt whether his "Theory of Biogenesis," which explains 

 development partly from an " evolutionistic " and partly from an " epigenetic " 

 standpoint, will be very widely received. We believe that many of Dr. 

 Hertwig's deductions are founded on unsound premises. For instance, we 

 hesitate to place very much value on the results of those experimental 

 embryologists, e.g., Loeb and Herbst, who submit developing organisms to 

 conditions seemingly impossible in a natural state. Their results are 

 interesting, and deserve to be carefully noted, but they can very easily be 

 made to prove too much, and then become exceedingly dangerous pitfalls 

 from which, in our opinion, Dr. Hertwig has not escaped. He is, however, 

 much to be congratulated in fighting shy of metaphysics and reserving 

 himself to the facts of embryology, cytology, and medicine and surgery, taken 

 from sources probably unknown to the general biologist ; while there can 

 be no doubt that a careful study of the work will open out many new paths of 

 research. Herein, we think, lies the great merit of the book. 



The first four chapters are devoted to a comprehensive study of the 

 cell in relation to its neighbours, and deals especially with the organic 

 connections between the cells composing the bodies of animals and plants. 

 The author then goes on to point out how many external forces there are 

 continually at work in the environment of an organism which produce 

 the most complicated effects on it, but these depend also on the nature 

 of the organism itself. The fact that fertilised ova of two very different forms 

 develop in what are apparently identical circumstances, shows that much 

 depends on the internal molecular structure of the ovum. This leads on 

 to a comparison of the rival theories of the "evolutionists" (Weismann, 



152 



