CASTLE. — INBREEDING, CROSS-BREEDING, AND SELECTION. 763 



An examination of these tables shows : 



(1) That a female of the A series mated with a male of series M or N 

 does not have her productiveness increased thereby. See Tables XV, 

 XVI, XVII, and XVIII. 



(2) That a female of series M or N mated with a male of the A series 

 does not have her productiveness diminished thereby. See Tables X, 

 XI, XII, XIII, and XIV. The reverse seems to be true in certain cases, 

 but this was probably due to the bestowal of special care upon the cross- 

 mated series. In the case of those recorded in Tables XI and XIII this 

 is almost certainly true ; the jars of cross-mated flies were in those two 

 instances transferred to a room warmer than that in which the pure M 

 and .V series were reared. 



TABLE XIII. 



Genealogy of N A Series. 



(Cross Ga, page 747 ; see also Tables XII and XIV.) 



N2 9 X A 31.5 



[376] 



[7] 



£ o §3 £ c 

 J= gee J= gr 



**• ai m 



NA 1 435 207 62 



NA 2 388 352 581 421 464 375 430 428 55 



NA 3 Fertile 243 307 272 Fertile 274 367 32 



It follows from (1) and (2) that low productiveness in Drosophila is 

 due to low productiveness of eggs, not of spermatozoa. Complete sterility, 

 however, may be found in either sex, as is shown by the history of both 

 the A and the M series. 



(3) The daughters of an A female by an M or an N male produce 

 more young than their mother did, and more than other A mothers do 

 under identical conditions. Their productiveness does not differ mate- 

 rially from that of purely mated M and N mothers, though complete 

 sterility may appear among them. 



(4) The daughters of an M or an N mother by an A male are on the 

 whole similar in productiveness to their mother and to purely mated M 

 and N mothers. None of the daughters has been found sterile. 



