TRANSITIONS IN MORPHOLOGICAL CHARACTERS 99 



Results in series bred from different members of a single family 



Early in the experiments the question arose whether, in the 

 selection of individuals as parents for pedigree lines, a physiologi- 

 cal difference might exist between the earlier and later individuals 

 produced by a single parent. This seemed the more probable 

 in that such differences have been claimed to be important in the 

 reproduction of certain minor Crustacea. To determine whether 

 such differences existed, a number of sister individuals, from the 

 fourth generation of D, were allowed to produce series of five gen- 

 erations each. These constituted separate minor pedigree series. 

 They showed no variation in the type of individuals produced. 

 One of these series bred from the ninth sister in a family of ten 

 and termed series D 2, was continued further to the seventieth 

 generation under conditions parallel to the general series A and D; 

 its history is given in table 3. The direct object of this added 

 series was to disclose, if possible, any latent weakness or difference 

 resulting even in the remoter generations of a series derived from 

 the later progeny. This series also furnishes another general 

 control to A and T>. We shall later show that differences do 

 exist between the earlier and later members of a single family. 

 But the results in this series show conclusively that such differ- 

 ences do not manifest themselves under the conditions present 

 throughout these experiments. 



Influence of size of parent on offspring 



The next possibility tested was as to whether the size of the 

 parent in any way influenced the size, form, or any other charac- 

 teristic of the progeny. From the eighth generation of series 

 D, young of different sizes were isolated. When they had devel- 

 oped to maturity four of the smallest and four of the largest were 

 brought together into two parallel mass cultures. In order that 

 all the conditions throughout the experiments should remain iden- 

 tical in the two cultures, partial exchanges of fluid were made 

 between them from time to time. After three weeks under these 

 conditions comparison of individuals from these two cultures 

 showed that the initial size difference had disappeared, the 



