xxxvi 



and lower, requires, so Nageli thought, to be modified and supple- 

 mented by the " Yervollkommnungstheorie," inherited from Lamarck, 

 according to which variation takes place determinately and in the 

 higher direction only. From this point of view, Nageli emphatically 

 asserted that the degree of variability which gives rise to more or 

 less constant varieties or races is the result, not of external, but of 

 internal, causes, an assertion which has since been strongly supported, 

 though on different grounds, by Weismann and others. 



The whole matter is fully discussed in his ' Mechanisch-physio- 

 logische Theorie der Abstainmungslehre,' published nearly twenty 

 years later, where, though there is greater elaboration, there is no 

 essential change of view. In this work Nageli introduces the idea 

 of a material basis for heredity in the form of what he terms " idio- 

 plasm." The characters w T hich an organism inherits from its parent 

 or parents are transmitted by the idioplasm of the reproductive cell 

 or cells, in which all the properties of the adult form are inherent. 

 But the idioplasm of any one generation is not identical with that of 

 either its predecessor or its successor. It is always increasing in 

 complexity as regards both the arrangement and the constitution of 

 its micellae, with the result that each generation marks an advance, 

 though not always an immediately appreciable one. But the varia- 

 tion which is primarily due to the inherent properties of the idio- 

 plasm is not altogether unaffected by external conditions ; when 

 these act continuously in a given direction they may cause modifica- 

 tions which are, however, merely adaptive. In a word, whereas, on 

 the Darwinian theory, all organisation is essentially adaptive, accord- 

 ing to Nageli the development of higher organisation and of more 

 complete division of labour is the visible expression of the spon- 

 taneous evolution of the idioplasm. 



Although Nageli's theory of evolution, as laid down in the ' Ab- 

 stamrnungslehre,' has not met with general acceptance, more particu- 

 larly as regards the small importance which he attaches to natural 

 selection, still the work as a whole cannot be judged as other than a 

 worthy close to the labours of its author. Full as it is of the accu- 

 mulated knowledge and experience of a long and earnest scientific 

 career, it constitutes one of the most valuable and suggestive recent 

 contributions to the theory of reproduction and descent. 



S. H. V. 



Philip Herbert Carpenter, the fourth son of Dr. W. B. Carpenter, 

 was born at Westminster, on February 6, 1852. He received his 

 earlier education at University College School ; and in 1871 commenced 

 residence at Cambridge as a scholar of Trinity College. He graduated 

 B.A. in 1874, in the First Class of the Natural Sciences Tripos, and 

 proceeded to the further degrees of M.A. in 1878, and D.Sc. in 1884. 



