Abstract
The egg-waters of the sand-dollar (Echinarachnius parma), starfish (Asterias forbesii), and sea-urchin (Arbacia punctulata), have been tested by electrophoresis for their effects on the sperm of each of these 3 species. Egg-water was routinely prepared by allowing freshly obtained eggs to stand a half-hour or more in contact with 0.5 M. NaCl adjusted with NaOH to an approximate pH of 8.2. This solution was filtered and mixed in equal volumes with suspensions of fresh sperm in 0.5 M. NaCl of pH 8.2. In 2 experiments the egg-water and sperm suspensions were both made with sea-water instead of NaCl solution. Later experiments showed that the exposure to 0.5 M. NaCl of pH 8.2 did not kill the sperm or the eggs from which the egg-waters were derived.
For agglutination the egg-water used was the same as in the corresponding electrophoresis experiment, but the sperm were suspended in sea-water. The agglutination technique was essentially that of Lillie and Just. 1
In the earlier experiments precautions to obtain the sperm and eggs free from perivisceral fluid were not taken; in the later experiments such precautions were taken. Differences in result due to such precautions were not noted.
Electrophoresis was conducted in a Northrop-Kunitz microcataphoresis cell 2 of a type described elsewhere. 3 Observations were made on sperm whose heads were in the focal plane.
Each of the sperm species studied was found to be negatively charged. In Table I are given the mean cataphoretic velocities with their probable errors, and the surface potential differences calculated from these velocities making the assumptions of Northrop and Cullen. 4 The values in Table I are all for control sperm suspensions before contact with egg-water.
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