148 Animal Life and Intelligence. 



is by fission. And if the cell which undergoes fission has 

 been modified, the two separate cell-organisms which result 

 from that fission will retain the special modification. In 

 such cases the transmission of acquired characters is readily 

 comprehensible. We have an hereditary summation of 

 effects. 



With the metazoa the case is different. In the higher 

 forms the germinal cells are internal and sheltered from 

 environing influences by the protecting body-wall. It is 

 the body-cells that react to environmental stresses; it is 

 muscle and nerve in which faculty is strengthened by use 

 and exercise, or allowed to dwindle through neglect. The 

 germ-cells are shielded from external influences. They 

 lead a sheltered and protected life within the body-cavity. 

 It is no part of their business to take part in either passive 

 resistance or responsive activity. During the individual 

 life, then, the body may be modified, may acquire new 

 tissue, may by exercise develop enhanced faculties. But 

 can the body so modified affect the germ-cells which it 

 carries within it ? 



Biologists are divided on this question. Some say that 

 the body cannot affect the germ ; others believe that it can 

 and does do so. 



It might seem an easy matter to settle one way or 

 another. But, in truth, it is by no means so easy. Suppose 

 that a man by strenuous exercise brings certain muscles to 

 a high degree of strength or co-ordination. His son takes 

 early to athletics, and perhaps excels his parent. Is this 

 a case of transmitted fibre and faculty ? It may be. But 

 how came it that the father took to athletics, and was 

 enabled to develop so lithe and powerful a frame ? It must 

 have been " in him," as we say. In other words, it must 

 have been a product of the germ-cells from which he was 

 developed. And since his son was developed, in part at 

 least, from a germ- cell continuous with these, what more 

 natural than that he too should have an inherent athletic 

 habit ? Every faculty that is developed in any individual 

 is potential in the germ-stuff from which he springs ; the 



