110 THE EGGS OF MAMMALS 



data) the writer has transplanted ova so activated into the 

 fallopian tubes of pseudopregnant rabbit does and has later 

 recovered the transplanted ova. A number had undergone 

 normal but obviously belated cleavage. A few cleaved at 

 the normal rate and about 10% of the total attained the 

 blastula stage. 



In order to obviate any undetected effects of the manipula- 

 tion of ova in vitro Pincus and Enzmann (1936a) undertook 

 the activation of ova in vivo by injecting into the tops of 

 rabbit fallopian tubes sperm suspensions previously irradi- 

 ated with ultraviolet light of 2357 A° wavelength. The does 

 used in these experiments had been mated to sterile bucks 

 12 to 13 hours previously so that their ovulated ova were 

 embedded in the follicle cell plug. Into one oviduct the 

 rayed sperm were injected, into the other an identical 

 sample of unrayed sperm. It was found that ova from the 

 tubes receiving unrayed sperm suspensions were for the 

 most part normally fertilized and cleaved at the normal 

 rate. Ova seminated with rayed sperm showed varying 

 proportions of normally cleavage stages depending upon the 

 time of exposure of the sperm to the ultraviolet light. Long 

 exposures resulted in a preponderance of irregularly cleaved 

 ova. But even the regularly cleaved ova resulting from 

 seminations of sperm given short exposures were markedly re- 

 tarded when compared with the control ova in the other tube. 



The ultraviolet treatment with the particular wavelength 

 used results presumably in the inactivation of the sperm 

 chromatin (see Swann and del Rosario, 1932), and depend- 

 ing on the time of exposure (e.g., intensity of radiation) 

 leaves the non-chromatic portions of the sperm relatively 

 unaffected. Dalq and Simon (1931) have shown that sperm 

 treated with ultraviolet light penetrate into the egg cyto- 

 plasm but pronucleus formation does not occur and the 

 chromatin disintegrates. If the sperm centrosome apparatus 

 is not inactivated normal cleavage occurs, otherwise irregular 

 development ensues. 



The data of Pincus (1930) indicate that parthenogenetic 



