316 STUDIES, SCIENTIFIC AND SOCIAL 



some experiments which led him to doubt the correctness 

 of Darwin's main contention — that minute gemmules 

 from every cell in the animal body were collected in each 

 of the germ and sperm cells, and thus led to the repro- 

 duction of a similar body. He transfused large quantities 

 of blood from black to white rabbits, and mcc versa, with- 

 out in any way injuring them ; and after this infusion of 

 blood from a very distinct variety, sometimes to the extent 

 of one-third of its whole amount, each kind bred as true 

 as before, showing no signs whatever of intermixture. 

 He then developed a new theory of heredity, which 

 appeared to him more in accordance with facts, and an 

 essential part of this theory was that the germinal material 

 passes direct from parent to offspring, instead of being 

 produced afresh from the various parts of the body ; and, 

 as a consequence,, changes produced in the body by 

 external agencies during its life will not be transmitted 

 to the offspring. A few years later Professor Weismann, 

 of Freiburg-in-Baden, independently arrived at a some- 

 what similar theory, founded on the embryological 

 researches of himself and other biologists ; and he sup- 

 ported it by such a body of evidence and by such a wealth 

 of illustration and reasoning that it at once attracted the 

 attention of biologists in ever}^ part of the world. This 

 theory being manifestly opposed to the inheritance of 

 acquired characters, he was led to examine the evidence 

 for this dogma, and found it to be extremely scanty, and 

 for the most part quite inconclusive. But as some biolo- 

 gists of great eminence believe that the inheritance of 

 such characters is absolutely necessary in order to explain 

 many of the phenomena of evolution, the discussion on 

 this point has been carried on by many who would have 

 felt little interest in the problem if it were one of embryo- 

 logical development alone. Year by year the question 

 has been discussed in books, pamphlets, and review articles, 

 while Professor Weismann has continued his studies on 

 the whole subject, and in a volume of which an English 

 translation has just appeared, has worked out his theory 

 in very minute detail, grappling iaivlj with all the various 

 phenomena to be explained, and thus putting the whole 



