TRANSFORMISM 225 



duced ? Now this may have seemed a conclusive 

 argument in 1883, but is it so conclusive to-day ? We 

 know that the cells and tissues are not isolated particles, 

 but that all are connected together by protoplasmic 

 filaments. We know that specialised nervous tissues 

 are not necessary for the transmission of an impulse 

 from a sensory to a motor surface, but that such an 

 impulse may be transmitted by undifferentiated proto- 

 plasm. We know that nerve-cells and nerve-fibres 

 are not structurally continuous with each other but 

 that the impulse leaps across gaps, so to speak. We 

 know that events that occur in one part of the body 

 of the mammal may affect other parts by means of 

 the liberation of a chemical substance, or hormone, 

 into the blood stream. It would be strange indeed 

 if a logical hypothesis capable of accounting for the 

 transmission of a particular change from the soma to 

 the germ could not be elaborated. 



But acquired characters were not really transmitted 

 after all. So those who clung to Weismannism argued 

 — an unnecessary task surely if this transmissibility 

 were inconceivable. We cannot discuss the evidence 

 here, and it is unnecessary that we should do so, since 

 it is all considered in the popular books on heredity. 

 There is an apparent consensus of opinion in these 

 books which should not influence the reader un- 

 familiar with zoological literature, nor obscure the 

 fact that many zoologists and botanists accept the 

 opposite conclusion. The discussion is all very tire- 

 some, but we may glean some results of positive value 

 from it. It is unquestionable that very few con- 

 clusive and adequate investigations have been made : 

 one cannot help noticing that the literature contains 

 an amount of controversy out of all proportion to the 

 amount of sound experimental and observational 



