2 g2 MYRA M. SAMPSON. 



In sea-urchins and in Nereis the iso-agglutinating masses re- 

 semble whirling swarms in which the spermatozoa either are not 

 oriented or are oriented with their heads forming the central 

 nucleus of the swarm. However, a pinwheel type of i so -agglutina- 

 tion can be obtained with stale Arbacia spermatozoa. The motility 

 of the latter is decidedly subnormal. It is possible that the vari- 

 ation in shape of agglutinated masses may be correlated with the 

 degree of motility of the spermatozoa which are involved. 



3. Unmistakable iso-agglutination can not be detected in any 

 of the following: Asterias ochracea, Asterina, Asterias forbesii, 

 Lepasterias ccqualis, Cinningia, Ishnochiton niagdalencnsis, Mo- 

 pall a muscosa, Crypto chit on, and Abalone. 



4. Two types of hetero-agglutination are here reported : toxic 

 "mass coagulation," similar to that described by Lillie (1913) for 

 Nereis and by Just (1919) for Echmarachnius, and a pinwheel 

 type in Katliariua tunicata, which bears a startling resemblance to 

 iso-agglutination in the same species. 



5. Hetero-agglutination occurs between spermatozoa of K. iuni- 

 cata and solutions of cytolyzed spermatozoa or of blood of either 

 S. purpuratus or of S. franciscanus. The reciprocal also occurs : 

 hetero-agglutination of spermatozoa of either 5". purpuratus or of 

 S. franciscanus by the blood of K. tunic at a. 



6. Hetero-agglutination of spermatozoa of Ishnochiton inagda- 

 Iciiensis may be produced by the blood of either S. purpuratus or of 

 S. franciscanus. The reciprocal may also be produced: hetero- 

 agglutination of spermatozoa of either 5\ purpuratus or of 5". 

 franciscanus by blood of Ishnochiton magdalenensis. 



REFERENCES. 



Buller, A. H. 



'oo The Fertilization Process in Echinoidea. Report of the British Asso- 

 ciation, 70th meeting, 387-388. 

 Glaser, 0. C. 



'14 A Qualitative Analysis of the Egg Secretions and Extracts of Arbacia 

 and Asterias. BIOL. BULL., XXVI., 367-86. 



Just, E. E. 



'15 An Experimental Analysis of Fertilization in Platynereis Megalops, 



BIOL. BULL., XXVIII., 93-"4- 



'19 The Fertilization Reaction in Echinarachnius parma. II., The Role of 

 Fertilizin in Straight and Cross-Fertilization. BIOL. BULL., XXXVL, 

 11-38. 



