518 FRANK R. LILLIE 



There are three categories of behavior exhibited by spermatozoa 

 that seem to me of importance for the problem of fertihzation, 

 because all are exhibited in reponse to egg secretions. These 

 are (1) activation, (2) aggregation, (3) agglutination. The phe- 

 nomena of activation are involved in those conditions that affect 

 the activity of spermatozoa. The phenomena of aggregation are 

 positive taxic responses, for the most past chemotactic. The 

 phenomena of agglutination are exhibited in the presence of sub- 

 stances that cause the spermatozoa to adhere in masses. In a 

 preliminary paper I have described some aspects of these phenom- 

 ena (Science, N. S., vol. 36, October 18, 1912). We may con- 

 sider the subject matter under these three heads. 



The spermatozoa of marine animals in which fertilization takes 

 place in the sea-water offer advantages for study probably greater 

 than those of any other forms, because the conditions of normal 

 activity are given in the sea-water itself, no secretions of accessory 

 glands either of the male or of the female being requisite. More- 

 over, the spermatozoa may be obtained in large quantities. They 

 offer, thus, material directly accessible to experimental work with 

 the simplest possible facilities. Among the forms available for 

 work, Nereis and Arbacia were soon found to be best adapted 

 because the breeding season extends through most of the summer 

 and they furnish material in large quantities. The present paper 

 is therefore confined almost exclusively to these forms. 



Suspensions of the spermatozoa in sea-water formed the mate- 

 rial for all of the experiments. The reactions vary somewhat 

 according to the density of the suspensions, and it may be impor- 

 tant in future experiments to find some quantitative method of 

 expressing the variations in density. But for the purposes of 

 this paper it will be sufficient to indicate the extremes as opales- 

 cent, milky and creamy, with intermediate qualifications. An 

 approximation to uniformity was attained in many of the experi- 

 ments by adding a certain number of drops of the dry sperm^ 

 to measured quantities of sea-water. 



^ By 'dry sperm' is meant the sperm as it comes from the testes without the ad- 

 mixture of fiuid. 



