CORRELATION OF THE DIFFERENT VARIATIONS.
These observations and experiments furnished unmistakable evidence of a high correlation of these variants in all three sea-urchins. From table 3 the size of eggs and the percentage of eggs with jelly envelopes may be compared; also in table 4 the rate of membrane formation and total cleavage. From the different experiments it was observed that the following characters and characteristics were closely cor related, namely: No. 1. Globular shape of all or nearly all of the eggs.
No. 2. Large percentage of the eggs with the jelly envelope. No. 3. Size of the eggs close to mode, with very little variation. No. 4. (a) Fertilization membrane formed in about 2 minutes.
(b) Large percentage of the eggs form a membrane. No. 5. (a) A rapid rate of first cleavage.
(b) A high percentage of cleavage.
No. 2. A low percentage of eggs with their jelly envelopes. No. 3. Eggs usually larger than mode, and much variation. No. 4. (a) Fertilization membranes slow to appear.
(b) Small percentage of eggs form membranes. No. 5. (a) Slow rate of first cleavage.
An adequate understanding of these variations can not be had without a knowledge of the results of experiments with aging germ cells. It is expected that such results will appear in a later publica tion, but at present I wish merely to point out the nature of some of the variants and to call attention to the marked range of differences in each of the variants in fresh germ-cells. If these facts are thoroughly appreci ated, not only will many conflicting results on the physiology of eggs and sperm disappear, but a clearer understanding of the situation may result.
A number of investigators have remarked on the fact that under apparently identical conditions varying experimental results were obtained, and have suggested that the differences were due to some physiologic difference in the eggs.
Stockard (7) stated "the fact that a number of eggs when subjected to the same solutions do not all respond in a like manner" was due to "differences in individual resistance and vigor."'
F. R. Lillie (2) noted that "the failure to obtain exactly the same curve * * * was due in part to the natural variability of different lots of eggs and sperm." Elsewhere he asserts that the percentage of cleavage was more dependent on the conditions of the sperm than upon its concentration.
J. Loeb and H. Wasteneys (5) believed that the different results on the effects of weak and strong bases on the oxidation of eggs of the sea-urchin may be due to differences in the eggs.
Wasteneys (8) later, in working upon the oxidation of sea-urchin eggs, concluded that the variations in his results were due to differences in sensitiveness of eggs of different females and perhaps to differences of temperature.
R. S. Lillie (3), from a study of the rate of swelling of eggs in diluted sea-water, also concluded that the variability in rate was due to the condition of the eggs.
In studying the fertilisin phenomenon, F. R. Lillie (1) arrived at a more adequate appreciation of the nature of this variability when he held that the condition of the eggs, whether ripe or immature, fresh or stale, with or without jelly, is more important than concentration of the eggs. Elsewhere (p. 568) he remarked that "the condition of the gonads is the most variable thing in summer sea-urchins." R. S. Lillie (3) made a notable contribution when he concluded that resistance to osmotic disruption in dilute sea-water was "a convenient index of the physiologic condition of the plasma membrane" and that "an intimate connection exists between the general physiologic con dition of the egg and the physiologic state of the plasma membrane." We are not justified in assuming that all ripe eggs freshly removed from the bodies of the sea-urchins are in a uniform or nearly uniform physiologic condition or that at a subsequent interval in sea-water the eggs continue to remain in a fairly uniform physiologic condition.