4 E. E. JUST. 



sea-water. Many developing eggs are devoid of jelly hull, but 

 the cortical changes are complete. 



One hour and ten minutes after exposure, some eggs are in 

 "blister" cleavages; that is, the protoplasm is irregularly budded. 

 One hour and thirty minutes to two hours after the change to 

 ordinary sea-water, among all gradations of cleavage-like patterns 

 are some normal two and four-cell stages. The next day, Nos. 3 

 to 10 showed some real cleavages and a small per cent, of ap- 

 parently normal swimming forms. Many are beaded or blis- 

 tered, some are unsegmented "swimmers," and some two and 

 four-cell swimming forms. Some eggs remain in the germinal 

 vesicle stage. 



(b) June 23, 11:00 A.M. A female placed in 50 c.c. of sea- 

 water at 35.5° C. is rendered immobile but does not shed. Eggs 

 are cut out at 11:02, the worm removed. Six samples of eggs 

 are taken as follows : ii:i8, 11:25, 11:34, 11:40, 11:45, 11:50. 



Many eggs on removal from the warm sea-water show the 

 jelly formed. The membranes after jelly formation are still a 

 little farther from the eggs than in normal fertilization. Many 

 eggs remain in the germinal vesicle stage with the cortex intact. 



1:45 P.M. Fairly normal cleavages in Nos. i to 4. 



June 24, 8:30 A.M. Swimming forms are found in the dishes. 

 By far the best are those in Nos. 2 and 3. 



The optimum time of exposure, therefore, lies between twenty- 

 three and thirty-two minutes. Later experiments showed that 

 the optimum exposure at 35° C. is at or near twenty-five minutes. 



(c) June 24, several experiments were run at various tem- 

 peratures. Those at 35° C. confirmed the findings of the previous 

 ones. Temperatures ranging from 30° C. to 31° C. give no results; 

 regardless of the length of exposure the eggs remain in the ger- 

 minal vesicle stage. 



The following experiment of June 24, at 33° C. is typical of a 

 number of repetitions at this temperature: 



(d) June 24, 11:15 A.M. A female placed in 25 c.c. of sea- 

 water at 33° C. swims actively without discharging eggs. Eggs 

 are cut out at 11:15 and samples taken at five-minute intervals 

 up to 11:50. The temperature is practically constant. The 

 samples taken are masses of eggs with the cortex wholly or (in 



