SPAWNING HABITS OF CUMINGIA TELLINOIDES. 421 



shock. As a case in point, if the tube forming annelid Hydroides 

 is removed from its shell and the exposed worm placed in a dish 

 of sea water it will spawn at once, the eggs or sperm seeming to 

 come from every nephridium of the body. This worm will 

 always spawn under these circumstances whether the gametes are 

 fully mature or not. Half-grown eggs are as readily spawned as 

 mature ones. Hydroides will spawn in the spring before any of 

 the eggs are even approximately mature. 



In like manner, Cumingia spawn readily in the laboratory. It 

 is only necessary to place them in a bowl of sea water and allow 

 them to remain undisturbed for half an hour or forty-five minutes. 

 They usually begin to spawn in half an hour. The gametes are 

 expelled through the dorsal siphon which is extended to a great 

 length. As the eggs or sperm accumulate in the siphon they are 

 thrown out forcibly by sudden whip-like contractions of these 

 organs. During the height of the breeding season it frequently 

 happens that every individual brought to the laboratory spawns. 

 It is not to be supposed that all would have spawned on that 

 particular day if left in their natural environment. There is then 

 something about the treatment which involves digging them from 

 the sand and subjecting them to various unusual disturbances 

 which stimulates spawning. It is safe to conclude that this 

 spawning stimulus is shock as in the case of Hydroides. 

 Spawning takes place just the same when sea water is allowed to 

 flow gently through the dish so that the accumulation of CO 2 is 

 not a factor. It is to be noted that shock is an abnormal stimulus. 

 It may be said again that laboratory experiments are frequently 

 unreliable guides to natural behavior and may lead to mis- 

 interpretation if depended upon too implicitly. 



CHEMICAL STIMULI. 



The question next arises: do the sexes stimulate each other in 

 any way? The question as to whether the females are stimulated 

 to spawn by the presence of the male and vice versa has frequently 

 been discussed in connection with various species. Some very 

 clear cases of the existence of such a chemical stimulus have 

 been discovered. This, for instance, is the case in Nereis limbata 

 as described by Lillie and Just. \Yhen placed together in a dish 



