VITALITY OF THE GAMETES OF CUMINGIA TELLINOIDES

¹ WABASH COLLEGE, SEESSEL FELLOW, YALE UNIVERSITY

I. The average longevity of Cumingia eggs when kept at a temperature of 20° to 22° C. is 10 to 12 hours as judged by time of fragmentation and ability to give a high percentage of normal embryos. The average longevity at 18.5° to 20° C. is 12 to 15 hours.

II. Approximately two per cent. of any lot of eggs may be defective as shown by their early fragmentation which occurs long before the rest.

III. The outstanding fact is the wide range of variation in the vitality and longevity of Cumingia eggs. The eggs of a single individual vary by four hours or approximately 25 per cent., while the eggs of different females vary in their longevity from six to twenty-six hours or over 400 per cent.

IV. Eggs in rare instances show deterioration at spawning, apparently due to long-time storage in the ducts of the gonads. Most lots of eggs when freshly spawned give from 97 to 100 per cent. cleavage and normal development.

V. The longevity of the best sperm in suspensions of 1/400 to 1/500 per cent. is 10 to 12 hours as judged by functional activity and ability to give 90 to 100 per cent. fertilization and normal development. In sperm suspensions of 1/2000 to 1/3000 per cent. it is 4 to 7 hours, but from 30 to 50 per cent. fertilization may frequently be expected from suspensions 7 to 12 hours old and 1 to 5 per cent. fertilization from suspensions 12 to 20 hours old.

VI. Spermatozoa in concentrated suspensions of 1 to 3 per cent. retain their vigor for many hours. They frequently give 90 to 100 per cent fertilization after twenty four to thirty six hours, and some individual spermatozoa live for four days, still showing faint contractions of the tail at intervals This preservation of the life of the spermatozoa is attributed to the presence in the water of CO₂ produced by the activity of the spermatozoa, or to hydrogen ion concentration.

VII. Spermatozoa after becoming quiescent show activation in the presence of eggs or egg water.