SUSCEPTIBILITY OF AMPHIBIAN OVA TO X-RAYS 427 



to this generation have arisen from exposed spermatogonia. It 

 is also possible that young spermatocytes of the first order are 

 so affected by irradiation that they degenerate instead of expand- 

 ing in the normal manner. Complex morphogenic processes 

 are doubtless active during the growth of the spermatocytes and 

 the substances governing these processes may be very sensitive. 

 Ovarian ova are similarly sensitive during the period of growth. 



The spermatocytes of the second order show few abnormalities 

 of form. Those exposed to the rays give rise to abnormal 

 spermatids and spermatozoa but do not themselves manifest, 

 as a rule, marked alterations. One would expect that the expos- 

 ure of the spermatocytes of the first order would cause these to 

 give rise to abnormal spermatocytes of the second order but 

 apparently, as a rule, the spermatocytes of the first order are 

 either destroyed by irradiation or affected in such a way that the 

 effects first become manifest in the granddaughter cells (sperma- 

 tids and spermatozoa.) 



Irradiation of the spermatids and spermatozoa usually does 

 not affect the external form and development of these cells; it 

 however has been shown that irradiated amphibian (Bardeen '07) 

 and mammalian spermatozoa (Regaud and Dubreuil '08) may 

 give rise to monstrocities in the ova which they fertilize. 



The nutritive syncytium of the seminal glands may presist 

 after the complete disappearance of the generative cells but 

 according to Regaud it is itself somewhat sensitive to the rays. 

 The effects noted in the nutritive syncytium may perhaps be 

 considered rather as secondary to injuries to the generative cells 

 than as primary effects of irradiation. Regaud, however, believes 

 that irradiation may produce in the syncytium a necrosis which 

 secondarily causes the death of generative cells situated within 

 its sphere of influence. 



After severe irradiation the interstitial cells of the testicle may 

 be injured although they are far more resistant than the genera- 

 tive cells. While Regaud believes the effects of irradiation on 

 the interstitial cells are probably direct it would seem possible 

 that they might be due to toxines produced by the necrosis of the 

 generative cells. The connective tissues, vessels and nerves of the 



