METABOLIC AND OTHER CHANGES AT FERTILIZATION 8l 



lO 3 



=^ 2 



/\J ^ _,_— — i-» "* ' 



10 20 30 40 50 60 70 



Time after fertilization orparthenogenetic 

 activation in minutes 



FIG. 14 



.3 



Change in volume of sea-urchin egg {Heniicetttrotus pulclierrimus), in 

 /Li" ~ 10*, after three minutes' immersion in 40% sea water + 60% distilled 

 water, at various times after fertilization. The point whose co-ordinates on 

 the middle curve are app. 2-5 X 10"^ ^^ and 5 min. therefore refers to an 

 egg which was placed in hypotonic sea water (for 3 min.), 5 min. after 

 fertilization. The rate of swelling at this time is lower than it is in eggs 

 which are examined earlier, or later, than 5 min. after fertilization. O, 

 normal fertilization; C.unfertilized eggs previously treated for 3 min. with 

 M-urea ; # , unfertilized eggs previously treated with butyric acid-sea water 

 for 30-50 sees. T^ C, 17. After Ishikawa (1954). 



(1-2) Negligible increase in permeability to water, ^ ^^^ 0-5 

 (u.), 0-6 (f.). C. variopedatus (Shapiro, 1939*). 



Compare the decline in Og uptake after fertilization in these eggs. 



(1.3) 8% reduction in vapour pressure 30 min. after f. R. 

 temporaria (Picken & Rothschild, 1948). 



(2) Rate of P entry from external medium (to which ^^p had been 

 added) 40 times greater in f. than in u. eggs. A. punctulata 

 (Abelson, 1947*, 1948*). 



The increase started 7-10 min. after f. i-6 X io~^M-4-6-dinitro- 

 o-cresol inhibited P uptake by a factor of 6 though it doubled Og up- 

 take and virtually inhibited division. 



(2.1) Rate of P entry from external medium (to which ^^P had 

 been added) 130-160 times as great in f. as in u. eggs (accumula- 

 tion, not exchange). S. purpiiratus (Brooks & Chambers, 1948*). 



(2.2) No increase in rate of P entry from external medium (to 



