300 



RADIATION BIOLOGY 



periods of time ranfj;iiiK up to six 

 (a) 



o 



H 

 Z 



o 

 o 



u. 



o 



UJ 



a 



3 

 2 



0-1 



2-3 3-4 

 INTERVAL 

 (O) 

 n DENDRASTER-CHASE- UV 



■ URECHIS -CHASE - UV 

 STRONGYLOCENTROTUS-GIESE 



2804 A, 1244/ergs/mm^ 



Dl PSEUDOCENTROTUS- MIWA et al., 

 BETA RAYS 



(b) 



■ P. AURELIA-KIMBALL a GAITHER 



2650 A, lOOO/ergs/mm^ 



□ R CAUDATUM -GIESE 



2650 A, 2000/ergs/mm 

 Fig. 8-1. Bar diagrams to show the rela- 

 tive importance of delay in various divi- 

 sion intervals after irradiation. The 

 data from the various authors v/as recal- 

 culated as time for the division interval 

 in question and this time was expressed 

 as a nudtiple of the control time for the 

 same interval, (a) Data (Chase, 1938; 

 Miwa et al., 1939a; Giese, 1938c) for the 

 first three cleavages of various marine 

 eggs. The eggs were irnuliated sliortly 

 before insemination, and 0-1 is the inter- 

 val between insemination and the first 

 cleavage. (6) Data for two different 

 species of Paramecium. The interval 

 0-1 is between irradiation and the first 

 division thereafter. (Giese, 1945b; Kim- 

 ball and Gaither, unpublished.) 



months. The e{i;frs kept in the cold 

 .sho\v(!d the .siinu; dciUiy in the first 

 fe\v di\isions as those allowed to 

 devek)p immediately at 25*'C. 

 Ho\vever, another effect, produc- 

 tion of ahnormal embryos, showed 

 recovery during the period in the 

 cold. Evans (lOoO) has confirmed 

 these results hut has found a some- 

 what different situation with 

 Arbacia eggs. Arbacia eggs irradi- 

 ated \vith low-intensity X rays 

 divide without further delay when 

 the irradiation ceases, which sug- 

 gests that recovery and inhibition 

 occur at nearly equal rates. How- 

 ever, the effects on later embryonic 

 development are more pronounced 

 after longer exposures, indicating 

 that the rates of recovery for the 

 two effects are quite different and 

 that recovery of division delay is 

 more rapid. 



There have been a number of re- 

 ports that marine eggs exposed to 

 ultraviolet show delay in cleavages 

 later than the first one after treat- 

 ment. Chase (1937, 1938), using a 

 quartz mercury arc and the eggs of 

 the marine worm Urechis caupo and 

 the sand dollar Dendraster excen- 

 tricus, found that several successive 

 divisions were affected when radia- 

 tion was given before fertilization. 

 Not all of Chase's data demonstrate 

 recovery but observations were ex- 

 tended over only the first few 

 cleavages. Giese (1938c), using 

 monochromatic ultraviolet, found 

 the same thing for Strongijloccnt- 

 rotus purpuratus. Sample cases 

 from Chase and Giese are shown 

 in Fig. 8-la. However, Giese 

 (1939b) irradiated the sperm of 



