462 



MARIE A. HIXRICHS. 



TABLE II. 



EFFECT OF ULTRAVIOLET RADIATION OF SPERM ON DEVELOPMENT. 



When eggs are exposed to ultraviolet radiation for I to 4 

 minutes, and are then fertilized by normal sperm, typically 

 60-80 per cent, of the resulting larvae are normal, 10-20 per cent, 

 show indications of recovery, about 10 per cent, are distinctly 

 inhibited, and about 10 per cent, are dead. When the exposures 

 exceed 5 minutes, the mortality rises to about 70 per cent., with 

 an even distribution of normal, inhibited, and recovered forms. 

 Long exposures interfere so seriously with cleavage that death 

 results in early stages. The controls may be in the blastula 

 stage, while the radiated eggs show irregular 2- and 4-cell stages. 



B. Differential Acclimation and Differential Recovery. Forms 

 showing differential acclimation, where exposures of sperm have 

 been slight enough to permit adjustment of the system (i.e., of 

 normal egg X radiated sperm) to new developmental conditions, 

 and forms showing differential recovery, where inhibition due to 

 radiation of either egg or sperm is merely transitory, show the 

 opposite type of development from those which are perma- 

 nently differentially inhibited. There may be merely an over- 

 developed oral lobe, with aboral arms normal (Figs. 25-26), or 

 the latter may appear smaller than normal (Fig. 27), or there 

 may also be evidence of regulation in the median anterior region, 

 as indicated by the spreading of the aboral arms (Figs. 27-28). 

 Sometimes the angle between the arms reaches 180 (Figs. 29-30). 



It is possible to obtain a good percentage of differential 

 acclimation by fertilizing normal eggs with sperm which have 



'Figures indicate the percentages of developing plutei which are normal (N.) 

 acclimated (Accl.), inhibited (Inh.), or dead (D.). 



