SOMATIC AND GENETIC STERILITY 57 



The autopsy findings were in accord with this expectation. 

 The sex organs were in a condition intermediate between laying 

 and non-laying condition; no anatomical obstruction to egg 

 laying was observed; there was no evidence that ovulation had 

 taken place into the body cavity. 



The case of No. 249 is to be regarded as one of nearly complete 

 genetic sterility. 



DISCUSSION 



In the present discussion the term ^somatic sterility' is used 

 to distinguish obstructions to egg-laying due to accidents or 

 disease affecting the individual, and not (so far as we have any 

 right to infer) inherited from her ancestors. A distinction is 

 made between sterility due to these causes, which may include 

 not only actual obstructive lesions of the genital organs, but 

 also a general lowering of the physiological tonus of the individual 

 to such an extent that it does not form yolk, and sterility due to 

 a lack of the genes for egg-production. 



The preceding paragraphs show that three of the four birds 

 which belonged to high laying strains and which did not fulfill 

 the expectation, based on a knowledge of their genetic constitu- 

 tion, failed because of the impossibility of a yolk entering the 

 oviduct. Two other birds belonging to segregating families 

 (one of these had proved herself a high producer by her own 

 winter record) showed the same reason for not aying. 



Another interesting observation is that four of the five birds 

 known to be ovulating into the body cavity because of some 

 obstructions to the mouth of the oviduct nested in rhythms 

 comparable to the laying rhythm of normal birds. One of the 

 authors (Pearl '12) has already published a similar record of 

 another 'zero^ bird belonging to a high laying line. There are 

 now several similar records on file. He called attention to the 

 fact that it has been experimentally shown at this laboratory 

 that in cases of ligation, transsection or entire removal of the 

 oviduct without injury to the ovary the 



* * * * bird goes regularly through the entire process of lay- 

 ing save for extrusion of an egg which is physically impossible. The 



