764 



INHERITANCE 



lions of new individuals are produced, all with body size partly de- 

 pendent on the q^toplasmic constitution. Similarly, the small body of B 

 is raised to the new size only slowly and gradually through many genera- 

 tions. The gradual change in size to an intermediate condition, which is 

 finally the same in both the clones, can be due only to the fact that after 

 conjugation the two ex-conjugants and their descendant clones are alike 

 in their nuclei. The nucleus gradually alters the cytoplasm, bringing the 



Figure 178. Different ultimate mean 

 sizes (numbered 1, 2, 3, 4 in each case) 

 reached by descendants of different pairs 

 from crosses of the same two races (A 

 and B, in each case). The results are 

 shown for four different crosses. To be 

 read as follows: at the upper left A and 

 B shows the mean sizes of two races 

 that were crossed. Four pairs of this 

 cross gave four stocks of the ultimate 

 mean sizes shown at 1, 2, 3, 4. Of the 

 next cross to the right four pairs were 

 similarly obtained, of the two others but 

 three. (Based on the measurements of 

 De Garis, 1935.) 



size in both clones ultimately to that which is characteristic for the nu- 

 clear constitution. 



Many such crosses between large and small races were made by De 

 Garis. In all cases the cytoplasm affects the size for many generations, 

 but finally the descendants of the two ex-conjugants come to a common 

 size, corresponding to the common nuclear constitution. The final size is, 

 however, not always midway between the sizes of the two conjugants of 

 the pair. In some cases it is much nearer to that of one of the two parental 

 clones than to that of the other. Such a case is illustrated in Figure 177. 

 In this, two clones were crossed, in which the mean lengths were re- 

 spectively 203 microns (clone A) and 81 microns (clone B). After the 

 gradual change in size through some 24 generations, the ultimate size 

 reached was much nearer to that of the smaller parent, B. Such results 

 were seen in many of De Garis's crosses (see Table 20). The ultimate 



