THE WONDER OF LIFE 597 



For that would be obviously very disadvantageous, and yet 

 we cannot have the one without the other, the pluses 

 without the minuses. 



All biologists are agreed that starving a mother may 

 prejudice the development of the offspring, and that the 

 accumulation of toxins in the body of either parent may 

 have the same effect, but that is not the point of the long- 

 continued and stiU unended controversy regarding the 

 transmission of somatic modifications (badly called ' the 

 inheritance of acquired characters'). The precise point 

 at issue is this : Does a structural change in a pa/rt of the 

 body, directly induced by use or disuse, or by some change in 

 surroundings and nurture generally, ever affect the germ- 

 plasm in the r&productive organs in such a specific or repre- 

 sentative way that the offspring will thereby exhibit the same 

 modification that the parent acquired, or even a tendency 

 towards it ? 



We have discussed this question carefully in our Hered- 

 ity and Darwinism and Human Life, and we shall 

 not attempt to sunmiarize the pros and cons. It may be of 

 interest, however, to give a short account of what appears 

 to us to be the most careful experimental contribution 

 that has yet been made towards the solution of this crucial 

 biological problem. We refer to Dr. W. E. Agar's experi- 

 ments on one of the small Crustacea, a Daphnid or 

 water-flea. The condensed narrative is necessarily a 

 Uttle difficult, but it wiH reward the serious student, not 

 only in its interesting conclusion, but also as a fine 

 example of scientific method. 



{E) A Test Case. — ^Dr. W. E. Agar studied a curious 

 abnormahty — ^reflexion of the valves of the carapace — ^in 

 the water-flea or Daphnid, called Simocephalus vetulus. 



