'^ CALIFOKNIA ACADEMY OP SCIENCES. 



lieredily have appeared, the second in 1891. Pi'of. 

 Weismann's views, although not entirely original, are 

 stated with such a rigid consistency to all the conse- 

 (luencus which they involve, are fraught with such un- 

 usual and daring speculations, and so vitally affect many 

 of our scientific dogmas, that they have caused a re- 

 markable revolution in the scientific world. By many 

 English biologists these new views have been received 

 with great favor. Wallace has thrown the weight of his 

 api)roval with them. With such avidity have they been 

 accepted that one is almost tempted to feel that a reac- 

 tion must ultimately follow. In America the case has 

 been directly the reverse. Instead of meeting with 

 favor they have been passed by in silence, questioned, 

 doubted, denied, and even in some cases treated almost 

 with scorn and ridicule. Against such an extreme as 

 this also, reaction seems inevitable. 



The chief value of ^\''eismann's work, regardless of 

 how correct or incorrect it iiiay ultimately prove to be, 

 is the fact that he has attacked the problem of heredity 

 from an entirely new point of view, and has set the sci- 

 entific world to thinking. It will be advisable to con- 

 sider his speculations in some detail, as bearing directly 

 upon the subject under discussion. 



Weismann commences his discussion with an inquiry 

 into the nature of death. He asks why mortality should 

 be a necessary consequence of life. In unicellular organ- 

 isms reproduction takes place by fission. The life of one 

 umceba cojiies to an end by the division of the parent into 

 two equal halves, each of which forms a new individual. 

 " But," as Weismann says, " this process cannot be truly 

 called death, ^\"here is the dead body? — what is it that 

 dies? Nothing dies ; the body of the animal only divides 

 into two similar parts, possessing the same constitution. 

 Each of these parts is exactly like its parent, lives in the 



