270 



MYRA M. SAMPSON. 



ripe eggs to secrete into two volumes of filtered sea-water for ten 

 minutes. The egg-water is then separated from the eggs by 

 filtration or centrifugation. The agglutination test is performed 

 as follows : A drop of i per cent, sperm suspension placed between 

 a slide and a cover glass supported by mm. glass rods spreads out 

 into a thin film, and in it the spermatozoa may be studied micro- 

 scopically. A fine-pointed capillary glass tube attached to rubber 

 tubing is used for blowing drops of test solutions into the thin 

 film of sperm suspension. 



3. ISO-AGGLUTINATION IN SEA-URCHINS. 



The results of my own experiments substantiate the statement 

 of F. R. Lillie (1919, 1921) that egg secretions of Arbacia, S. 

 purpuratus, and 5. franciscanus produce three effects on species- 

 true spermatozoa : activation, stimulation to increased motility fol- 

 lowed later by a state of rest ; aggregation, a tropistic phenomenon 

 occurring only when there is a gradient from the egg-secretion to 

 the spermatozoa ; and agglutination. 



Iso-agglutination Reaction*. 



An immediate and intense activation and the aggregation of the 

 spermatozoa into a dense ring around the injected drop of egg- 

 water is followed by the agglutination reaction. The ring rapidly 

 becomes beaded in appearance and ultimately breaks up into small 

 swarms. In each of the latter the spermatozoa are in such rapid 

 motion that the entire swarm whirls about. Simultaneously simi- 

 lar smaller swarms form from the few spermatozoa trapped within 

 the enclosed drop. For a brief period the swarms appear to rush 

 together to form larger masses. The movements of the sperma- 

 tozoa gradually slacken, and after a short interval, depending on 

 the size of the swarms, a reversal occurs. They break up and in 

 a short time the spermatozoa are dispersed, less active than origi- 

 nally. 



In a special series of experiments I used spermatozoa of Arbacia 

 from 25 per cent, and 50 per cent, suspensions which had stood at 

 room temperature (21 C.) for from twelve to twenty-four hours, 

 and were then aerated to remove the carbon dioxide, which in 

 itself might affect the agglutination process. In i per cent, sus- 



