166 ROSCOE R. HYDE 



in character in that it is strongly transmissible through inheri- 

 tance, behaving like a character that segregates. The evidence 

 goes to show that the character in all probability is not carried by 

 the X-chromosome. (3) The sterility as it affects the female 

 can be eliminated by selection. Inbreeding, as such, does not 

 appear to be the causative agent in producing this kind of sterility. 



A close study of the females revealed the fact that they were 

 not laying eggs. The abdomen swelled until it was very large 

 and in many cases the ovipositor protruded some distance beyond 

 the body. The female could not deposit her eggs. A score or 

 more females were sectioned and these sections showed eggs 

 present in abundance. In fact, a mere examination of the fly 

 after it had been mashed on a glass slide showed in all cases, ap- 

 parently well-formed eggs in large numbers. I have examined 

 scores in this manner after they had been tested with a number 

 of males and except only one doubtful case I have found that all 

 had eggs. The exact nature of the defect cannot be stated until 

 more attention is given to a study of sections, but the defect is of 

 such a kind that it prevents her from laying her eggs. The possi- 

 bility that parasites were the source of the trouble suggested 

 itself. Sections show, however, that these flies are remarkably 

 free from parasites in so far as one can make out with ordinary 

 stains, and the behavior of sterility in transmission, moreover, 

 shows the futility of such an hypothesis. 



In the case of the fertile female one has merely to bring pressure 

 to bear upon the abdomen to cause her to expel an egg. The 

 sterile females will not respond to such treatment. On the con- 

 trary, the wall of the abdomen will burst, and allow the eggs to 

 roll out, while none will pass through the oviduct. Whether or 

 not the eggs are ever fertilized I cannot say. I have frequently 

 seen the sterile female copulate and I have planted scores of eggs 

 (obtained by opening the female) on banana but never has a single 

 larv^ emerged. 1 All attempts at artificial fertilization proved a 

 failure. 



1 A fertile female placed on a very poor grade of banana may refuse to lay her 

 eggs for some time. She holds them as long as she can but after a few days will 

 lay theYn. 



