440 



L. V. HEILBRUNN 



Five-second tests. Nereis. 



TABLE 13 

 Eggs fertilized at 10.55 a.m. 

 VI., 23.7°; at 12.20 -p.m. 24.9° 



Tem'perature at 11.11 



TIME AFTER 

 FERTILIZATIOM 



OBSERVATIONS 



2 



5 



8 

 11 

 14 



17 



20 

 23 

 26 

 29 

 32 

 35 

 38 



41 

 44 

 47 

 50 

 53 

 56 



62 



65 



67 



67J 



68 



681 



69 



70 



No hyaline zone. Germinal vesicle present. 



No hyaline zone. Germinal vesicle present. 



No hyaline zone. Germinal vesicle nearly faded out. 



Hyaline zone beginning to appear. No germinal vesicle. . 



Hyaline zone appears plainly; it extends through about one-fifth of 



egg. 

 Hyaline zone not pronounced. In some eggs it is absent; in others, 



if present, it is indicated rather than shown plainly. 

 Hyaline zone is absent generally (perhaps it is indicated in a few). 

 Hyaline zone plain. About one-fifth. 

 Hyaline zone appears plainly. 



Hyaline zone can be seen, but in most cases it is indistinct. 

 Hyaline zone can be seen, it is generally narrow and not distinct. 

 Generally no hyaline zone. 

 Hyaline zone present. It is generally narrow, but distinct and 



clear. 

 Hyaline zone plain, extending through one-fifth of egg. 

 Hyaline zone narrow if present at all. 

 No hyaline zone. 

 No hyaline zone. 

 No hyaline zone. 

 In many eggs hyaline zone is wide, clear, plain. It extends through 



one-fourth of egg, and its inner margin is almost at the equator. 

 Hyaline zone wide and clear as in previous test. 

 No hyaline zone in any eggs. 

 Segmentation beginning generally. 

 5/50 segmented completely. 

 8/25 segmented completely. 

 17/25 segmented completely. 

 21 /25 segmented completely. 

 49 /50 segmented completely. 



cleavage division.'' Of the first three periods of increased vis- 

 cosity the third, as might be expected, is the longest. It cor- 

 responds to the second period of increased viscosity in the 

 Cumingia egg. 



■• According to Wilson ('92), the first polar body is formed thirty-five to forty 

 minutes after fertilization, the second polar body ten to twelve minutes later, and 

 the egg divides after about seventy-five minutes. ' Evidently Wilson worked at 

 about the temperature of the above experiment. At lower temperatures the times 

 are of course longer. 



