April 18, 1902.] 



SCIENCE. 



621 



To tliose who can read tlie signs of the 

 times it is most evident that zoology has been 

 passing through a period of revolution during 

 the past ten years. A strong reaction has set 

 in against the extremely speculative theories 

 as to the factors of evolution, the inheritance 

 or non-inheritance of acquired characters, and 

 the whole 'phylogeny business' of a dozen 

 years ago. The present attitude of most zool- 

 ogists is more critical, less argumentative and 

 in all respects more wholesome than prevailed 

 when sky-scraping theories were erected on a 

 single square foot of fact. In this wholesome 

 reaction experimental morphology has played 

 a most important part; in fact, it was the 

 attempt to make biology an experimental sci- 

 ence which first aroused interest in this sub- 

 ject, and while at times some of these experi- 

 mental niorphologists have illustrated the 

 uncritical methods which they have denounced, 

 while their conclusions have often been open 

 to the criticism of having been hasty and 

 ephemeral, no one can deny the fact that their 

 work has introduced a new spirit into the 

 study of zoology. 



In this work the author has been one of the 

 most productive and at the same time one of 

 the most careful investigators. He saw, as 

 apparently few others did, that the develop- 

 ment of fragments of eggs and embryos was 

 at bottom the same problem as the regenera- 

 tion of parts of adult organisms, and during 

 the past ten years he and his pupils have done 

 a surprising amount of work on the regenera- 

 tion of embryos and adults. There is prob- 

 ably no other living man so well fitted to treat 

 this subject. To almost every topic discussed 

 in the book, save the ones on regeneration in 

 plants and on hj^pertrophy and atrophy, the 

 author has made important original contribu- 

 tions. The literature list at the end of the 

 book, which is very complete, covering the 

 most important papers on regeneration from 

 the time of Aristotle to the present day, in- 

 cludes 470 titles, and one tenth of this total 

 list has been contributed by Morgan and his 

 pupils. As a result the discussion of each 

 topic evinces a thoroughness of treatment and 

 a ripeness of judgment which could come only 

 from long and intimate acquaintance with 



the problems involved. The book is therefore 

 not merely a summary of the work which has 

 been done on regeneration, but it is also a 

 splendid contribution to knowledge. 



In the fourteen chapters of the book the 

 following subjects are presented: An histor- 

 ical and general introduction, the external and 

 internal factors of regeneration in animals, 

 regeneration in plants, a discussion of the 

 supposed relation between regeneration and 

 liability to injury, regeneration of internal 

 organs, physiological regeneration, fission, 

 budding and autotomy, grafting, origin of 

 new cells and tissues, regeneration in egg and 

 embryo, theories of development and of regen- 

 eration, general considerations on organiza- 

 tion, vitalism and teleology. Of these topics 

 the ones on regeneration and liability to in- 

 jury, regeneration in egg and embryo, theories 

 of regeneration and of development and the 

 general considerations are of most general 

 interest. 



The greater part of the chapter on regenera- 

 tion and liability to injury has already ap- 

 peared in Science, and it need only be said 

 here that Morgan has established in the most 

 convincing manner the fact that there is no 

 causal relation between the two, and that 

 therefore it is impossible to regard the won- 

 derful adaptations of regeneration as a result 

 of the action of natural selection. It has long 

 been recognized that natural selection is not 

 so much a theory of evolution as an attempt 

 to explain on causal grounds the remarkable 

 and exquisite adaptations shown by living 

 things. Nowhere are such adaptations more 

 striking than in regeneration, and yet here it 

 is in some cases quite certain that such adap- 

 tations cannot be attributed to the action of 

 the Darwinian or of the Lamarckian princi- 

 ple. All theories which attempt to explain 

 adaptations hold that they are due to experi- 

 ence; Lamarekism, that they are the direct 

 result of use, disuse and need ; Darwinism, that 

 they are the indirect result of experience 

 through the survival of the fittest. No theory 

 yet advanced can explain adaptations to con- 

 ditions never experienced before, and yet in 

 the regeneration of animals there are adapta- 

 tions which are undoubtedly of this sort. The 



