mother gives rise to the Une ending in sexual females, and 

 another stem-mother to the line ending in the males. On 

 the other hand in other species of Phylloxera and in many 

 aphids the same stem-mother produces both lines. 



In this connection it is interesting to observe the pro- 

 duction of males and females among bees, wasps and ants. 

 It is well known that fertilized eggs of the queen bee pro- 

 duce females and unfertilized eggs males. The mature egg 

 has one sex chromosome and the male cell has but one. 

 When the egg is fertilized by a male cell the product has 

 two sex chromosomes, characteristic of the cells of a female 

 bee; when unfertilized the egg develops into a male. 



Nature and Nurture Again. — "According to Mendel's 

 law certain ancestors contribute nothing to the constitution 

 of certain offspring in respect of certain characters " (Lock) , 

 hence all individuals of a race may and often do not possess 

 the same characters. Neither are the differences between 

 individuals of the same race always the result of unequal 

 development of the characters or even of their latency, 



A distinction is here made between racial and varietal 

 characters, but no matter how it is composed "every inheri- 

 tance requires an appropriate nurture if it is to realize itself 

 in development. Nurture supplies the liberating stimuli 

 necessary for the fuller expression of the inheritance" 

 (Thomson). 



It is often difficult to say which is the more important 

 factor in the life of the organism — Nature or Nurture. The 

 organism is dependent upon its surroundings for its develop- 

 ment. In unappropriate, unfavorable surroundings the 

 natural inheritance cannot find expression for its highest 

 possibilities. On the other hand the highest development 

 cannot be attained even in the best environment by an 

 organism with poor natural inheritance (See section "Eu- 

 genics"). 



In Mendelian inheritance every character is represent- 

 ed by one or more determiners or factors. This idea may 

 profitably be introduced into the discussion of Nature and 

 Nurture. Here, however, it must be assumed that there are 

 two sets of factors — those of environment and those of in- 

 heritance — every character being the product of these two 

 sets of factors. If either set be altered the organism will be 

 altered, that is, there will be variation. "Only those char- 

 acters appear regularly in successive generations which 



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