272 MYRA M. SAMPSON. 



jected drop of egg-water where the spermatozoa are less concen- 

 trated it is possible to observe the process of formation of these 

 pinwheels. A few spermatozoa first stick together in a group 

 without any apparent orientation and without enough motility to 

 produce whirling of the group. The three-dimensional pinwheels 

 form instantly, including these clumps within the wheel. A fusion 

 of pinwheels ensues for a short period. A complete reversal then 

 occurs in some, whereas other pinwheels remain permanent. A 

 protocol of one experiment will illustrate the time relations of the 

 phenomenon. 



E.vp. 616. Material: Doubly filtered standard egg-water of K. tunicata; 

 fresh i per cent, sperm suspension of K. tunicata. 

 5-27/21. 



3.15. Sperm suspension in sea-water spermatozoa slightly active. 



3.15. Inject a drop of egg-water 



Immediate intense activation. 

 Immediate ring formation. 



3.16. Formation of small clumps of spermatozoa. 

 3.165. Formation of three-dimensional pinwheels. 



3.17. Fusion of three-dimensional pinwheels. 

 3.19. Complete reversal of some pinwheels. 



3.25. Decrease in activity ; many permanent pinwheels remain. 



3.40. No change. 



5.00. No change. Spermatozoa still more active than originally. 



On May 28 I obtained with animals brought in on the preceding 

 day decided activation and ring formation, but no agglutination. 

 In previous tests on spermatozoa of this species I had discovered 

 that in order to obtain satisfactory results animals must be used 

 on the day on which they are obtained. During June and July of 

 1921 and 1922 additional experiments were conducted for me by 

 Dr. Van Wagenen. She reports results similar to those recorded 

 in Exp. 616. However, complete reversal of agglutination was 

 obtained with both standard egg-water and with the latter diluted 

 ten times. Dilutions of % o an d "/ooo produced activation but no 

 agglutination, thus indicating a rapid loss of agglutinating power 

 with dilution. 



5. ISO-AGGLUTINATION IN OTHER ECHINODERMS AND MOLLUSCS. 



Iso-agglutination tests were made upon the spermatozoa of 



certain other Echinoderms and Molluscs : Asterias ochracca, 



