BREEDING HABITS OF HETERONEREIS. I5I 



sperm to the water containing the female will usually cause 

 shedding of the eggs. 



There is thus a very precise form of sexual behavior which was 

 tested and demonstrated repeatedly during the seasons of 1911 

 and 1912. No attempt has been made to study the subject at 

 all exhaustively as our attention was directed to other problems, 

 but a few experiments were made dealing with the male reflex 

 that throw some more light on the matter. 



In the first place it is probable that the emanation of the female 

 that incites the male to shed sperm comes mainly from the eggs. 

 This could be shown in two ways: (i) Spent females, i. e., those 

 that have shed their eggs, do not produce the inciting substance 

 in quantities comparable to the production of egg-bearing 

 females. It was possible to obtain some effects by keeping four 

 or five spent females in a small quantity of sea -water over night; 

 but the effect on the male was so slight as probably to be attribut- 

 able to the few remaining eggs In the female, or to egg secretions 

 persisting In their bodies. Moreover mature males would not 

 respond to the presence of immature atokous females. (2) The 

 eggs alone produce the inciting substance quite rapidly; thus 

 in one experiment about one third of the eggs of a single female 

 charged about 10 c.c. of sea-water in 80 minutes so that a male shed 

 sperm quite freely on being put in some of this water. Transferring 

 to successive bowls of sea-water caused no reaction. The same 

 male shed yet more freely on being transferred to the same 

 quantity of sea-water from a bowl of 125 c.c. in which a mature 

 female had stood over night. This was repeated with several 

 variations always with positive results. 



The tests showed that the eggs alone were considerably more 

 effective than the spent females. The production of the stimu- 

 lating substance should therefore be attributed mainly to the 

 eggs. 



The problem of the nature of the emanation that stimulates 

 the males has received Inadequate attention; but some experi- 

 ments were made which narrow the field down considerably. 

 In the first place the reaction Is not due to the CO2 excretion of 

 the females. This follows from the fact that males do not produce 

 any stimulating substance, though they excrete CO2. A series 



