SPERM FILTRATES AND DIALYZATES

THEIR ACTION ON OVA OF THE SAME SPECIES

¹ DEPARTMENT OF ZOÖLOGY, UNIVERSITY OF MICHIGAN, AND SMITH COLLEGE, A. A. U. W.—BOSTON ALUMNÆ FELLOW

1. Solutions obtained by filtration and dialysis of suspensions of living sperm in sea-water activate ova of the same species.

2. Tests indicate that the effect is produced by some substance derived from the sperm, and not by some extraneous parthenogenetic factor.

3. Ova of Nereis exposed to specific sperm filtrates form fertilization membranes, complete their maturation and some develop into abnormal trochophores. Ova of sea-urchins fail to form membranes but do undergo nuclear and cell division.

4. Ova exposed to filtrates and dialyzates are rendered more susceptible to the action of hypertonic sea-water, and to the entrance of sperm.

5. In normal fertilization sperm exposed to "fertilizin" undergo profound modification in chemical structure and organization; and unless such modification occurs the sperm fail to fertilize the egg, even though they may enter it. It is possible that substances localized in the surface of the sperm head activate the ovum. Such localization is transitory.

6. Such substances, when given off by sperm into sea-water or egg-water, either because of dilution, decomposition, or admixture with waste products given off by sperm, produce definite changes in such ova, but are unable to effect complete activation of ova of the same species.