ORGANIC DIFFERENTIATION 87 



eggs of bees which develop without fertilization always produce 

 males. 



It is not our purpose here to study the problem of sex- 

 determination ; it must suffice if we have shown the importance 

 of the part played by the chromatin and indicated the bearing 

 it has upon a clear conception of the phenomena of heredity. 

 Furthermore, if in certain cases, most frequent in connexion with 

 insects, sex is determined from the time of the fecundation of 

 the egg and is specifically connected with certain conditions 

 in the formation of the spermatozoa, and even if this 

 determination in other cases is precocious, that is no reason 

 why we should assume that it is impossible to influence sex- 

 determination, or that we should abandon the problem 

 forthwith. 



Summing up, we may assert that the evolution of the ovum 

 can be classed as a phenomenon of nutrition. The reappearance 

 of the characters of parents in their offspring is called heredity. 

 No true explanation of the matter has yet been given. All that 

 has been asserted about it is either pure hypothesis or a begging 

 of the question, and the best that we can do for the present is 

 to attempt to narrow down the conditions in which heredity 

 first could have arisen, and once established, those in which it 

 functions. 1 



After what has been said of the theory of Weismann we 

 need not stop here to discuss his rejection of the inheritance 

 of acquired characters. This rejection is meaningless. It 

 must be admitted that living organisms have been modified 

 since the beginning of time ; that they have only been modified 

 by the acquisition of new characters, and that had these 

 characters not been hereditary, their modifications would not 

 have been preserved. The only problem with which we need 

 concern ourselves is to find out how these new characters have 

 been acquired. They have not arisen of their own accord — 

 unless we are face to face with a miracle — and yet, on the other 

 hand, it is undeniable that drought, humidity, a stronger or 

 weaker wind-action, heat, light, and even electricity can 

 modify, either temporarily or permanently, the individual 

 characters of living beings, be they animals or plants. The 

 nature of the food consumed and its superabundance or 

 scarcity have a still greater influence. If we cannot yet afford 



1 XXXVII. 



