242 
ZOOLOGY: A. J. GOLDFARB 
bility of eggs and sperm removed immediately after receiving the freshly 
collected sea urchins. For this purpose three different species of sea 
urchin were studied, namely, Toxopneustes and Hipponoe, of the shal- 
low tropical waters of the Dry Tortugas, Florida, and Arhacia of the 
deeper colder waters of Woods Hole, Mass. 
To obtain optimum conditions as nearly uniform as possible, pre- 
liminary experiments were made with each species. These experi- 
ments established the optimum concentration of fresh eggs and of fresh 
sperm for a given surface and volume of filtered sea water. For ex- 
ample about 800 eggs in 10 cc. of sea water, in Syracuse dishes, with 
0.05% sperm, with care exercised to avoid evaporation, gave optimum 
results with Toxopneustes and Arhacia. For Hipponoe the same condi- 
tions sufficed except that much greater concentration of sperm was 
needed. 
Having ascertained the optimum and constant conditions it was found 
that the remaining variability was in large measure a function of the 
particular male and female used. If cleavage be used as a measure 
of variability and if the eggs of a female be fertilized by different males, 
widely varying percentages of cleavage occurred. The female whose 
eggs gave the highest percent of cleavage by one male, usually gave 
the highest percent by other males, though the absolute percentage 
differed considerably. And vice versa a low cleavage female usually 
gave low cleavage by other males. A few experiments are cited to 
show some of the details (table 1). 
With these facts in mind a detailed study of certain variations were 
made as follows: (a) variations in size and shape of the eggs; (b) varia- 
tion in the jelly layer of eggs; (c) variation in membrane formation; 
(d) variation in cleavage. 
{a) Eggs of a considerable number of females of each species were 
carefully measured. The eggs of some females varied Kttle from the 
norm, others varied much, usually by enlargement. One set of read- 
ings of two females collected and prepared at the same time is given 
below. 
Ocular readings of diameter of eggs 
9 21 20.5 20 19.5 19 18.5 
1 0 0 0 0 33% 67% 
2 8% 24% 48% 24% 0 0 
Female number 1, varied but little from the norm (19); female num- 
ber 2 showed considerable enlargement, and variability. Eggs normal 
or nearly normal in size tended to be all or nearly all globular, eggs 
showing considerable variation tended to be elliptical. 
