26 SUMMAKY OF CURRENT RESEARCHES RELATING TO 



These he distinguishes as genetic variations and acquired modifications, 

 or, as many would now say, simply variations and modifications. Later 

 on he speaks also of " acquired variations." 



After pointing out that genetic variation is generally, if not essen- 

 tially, connected with sexual reproduction, he considers the features of 

 this process, distinguishing : — (a) the real reproductive act, which is the 

 division by fission of the parent into two unequal parts, one of which 

 continues to be calltd the parent, while the other is the gamete; and 

 (b~) the subsequent conjugation-process, in which a new individuality is 

 formed by the fusion of the distinct individualities of two gametes. The 

 phenomenon of sex, with all its associated complications, is merely a 

 device to ensure the coming together of the two gametes. 



Impressed by the fact that every acquired character presupposes a 

 congenital possibility of acquiring it, Mr. Sedgwick observes that " every 

 feature which successively appears in an organism in the march from the 

 uninucleatcd zygote to death is an acquired character." This, however, 

 is a new usage, and seems somewhat inconsistent with the previous 

 classification of observed differences into (a) congenital variations, and 

 (6) acquired characters ; for while the subject with which Mr. Sedgwick 

 started was variation, at this stage he discusses the development of all 

 the characters of the organism. What others call acquired characters he 

 would call variations in the acquired characters. "A genetic character 

 is the possibility of acquiring a ceitaiu feature under the influence 

 of a certain stimulus; it is not the feature itself — that is an acquired 

 character — but it is the possibility of producing the feature." "A 

 genet'c character is a character which depends upon the nature of the 

 organism, while an acquired character depends on the nature of the 

 stimulus." Would it not be clearer to return to the old distinction 

 between variation and modification ? 



The author points out the difficulty of conceiving the mechanism 

 whereby a modification of, say, the right arm, could be transmitted. 

 That changed conditions may have an effect upon the reproductive 

 organs is admitted ; but he thinks that the only effects which can be 

 spoken of with certainty are (o) the production of sterility, and (6) an 

 increase in genetic variability. 



Keturning to the question, Are genetic variations ever found in 

 asexual reproduction ? Mr. Sedgwick inclines to answer in the negative. 

 " If any indefinite variability, recalling genetic variability, makes its 

 appearance, it must be part of the genetic variability, and directly trace- 

 able to the zygote from which the asexual generations started." This 

 is opposed to Weismanu's view that nutritive changes in the body may 

 induce variations in the germ-plasm . 



In considering modifications of the reproductive organs in cases of 

 asexual reproduction, he asks three questions : — Will the modification 

 in the offspring have any adaptive relation whatever to the external 

 cause? (Probably not.) Will all the forms subjected to the modifying 

 influence be affected in the same way ? (Presumably they will.) . Will 

 the modification last beyond the life of the individuals produced by the 

 affected reproductive organ? (No data for decision.) 



Using the word heredity as equivalent to genetic resemblance, he 

 proceeds to point out that "heredity is really applicable only to the 



