182 EEPOKT— 1891. 



theories. To my mind these phenomena of " bud- variation " 

 are destructive of Weismann's view of the extreme importance 

 to variation of sexual reproduction, since they prove that 

 organisms luay develope marked variations of a permanent 

 character when sexual reproduction is altogether suspended. 

 And equally important in this connection, as has been pointed 

 out by Professor Vines,''' is the case of the numerous groups of 

 Fungi, presenting innumerable form-varieties, in which there 

 occurs no form of sexual reproduction. 



Weismann's ideas are so admirably marshalled and so 

 clearly expressed that his essaj's form a most interesting con- 

 tribution to the literature of biology. Moreover, anj-- work 

 which has excited so much discussion of the fundamental 

 problems of biological science can scarcely fail to lead to the 

 attainment of new truths or the elimination of old errors. 

 Perhaps the chief service which the author has rendered to 

 science by the publication of his essays has been in directing 

 attention, by the searching character of his criticism, to the 

 necessity for more conclusive evidence regarding the inherit- 

 ance of acquired characters. 



Written from a very different standpoint is the contribution 

 to the subject of the evolution of organisms recently put 

 forward by Eimer.j His object has been, by the careful study 

 of the variation of certain animals, to endeavour to find a 

 general law of variation. " The Darwinian principle of 

 utility," he writes, " the selection of the useful in the struggle 

 for existence, does not explain the first origin of new charac- 

 ters." "The unreserved study of a single species of animal has 

 led me to the discovery of a whole series of laws which the 

 extension of the investigation to other species showed to hold 

 good generally." " I v.'as able," to quote further from his In- 

 troduction, "to demonstrate that variation everywhere takes 

 place in quite definite directions which are few in number ; and 

 I was able, on the basis of my observations, to put forward the 

 view that the causes which lead to the formation of new 

 characters in organisms, and, in the last result, to their evolu- 

 tion, consist essentially in the chemico-physiological interac- 

 tion between the materitil composition of the body and external 

 influences." 



These results he arrived at by a study at first of the varia- 

 tions of the European wall-lizard [Lacerta vmralis), then after- 

 wards of those of other animals (mammals, birds, and insects), 

 the resul'ts being mainly derived from a study of the external 

 markings. His study of the wall-lizard led him to the conclu- 



* " An Examination of some Points in Professor Weismann's Theory 

 of Heredity:" Nature, Vol. 40 (1889). 

 I " Organic Evolution." 



