REPORT OF COMMISSIONERS OF INLAND FISHERIES. 191 



water, had they not been returned to the water at the end of each 

 successive test. 



Contact-irritability. — In the preceding section we have considered 

 merely the phototactic and the pliotopathic reactions, together with 

 soma points of tlieir inter-relation. It may now be of interest to 

 examine briefly that response of the lobsters to solid portions of 

 their immediate physical environment which, for the present lack of 

 a better term, we may call contact-irritability. 



It might reasonably be imagined that the loss of the swimming 

 branches (exopodites) of the thoracic appendages, which takes place 

 with the entrance to the fourth stage, would at once determine a 

 very radical change in the habits of the lobster larva? from that 

 time. We might surmise that the larvie would at once abandon 

 their pelagic manner of existence and enter at once upon a more 

 sedentary life among the rocks and weeds of the sea bottom. But 

 this is by no means the case, for never in the life history of the 

 lobster do we find them more able and persistent "swimmers" than 

 in the fourth stage of their existence, and just after the loss of those 

 ver}'' accessories, without which swimming would have been impos- 

 sible for them in any of the earlier stages. This energetic surface 

 swimming of the fourth-stage larvae was evident from many obser- 

 vations. One such case is especially noteworthy. In July a steam 

 launch, of which the captain had lost control, rammed one of the 

 floats which suspended six large hatching bags containing lobsters 

 in various stages. As a result of this accident a very large number 

 of fourth-stage larvse were suddenl}'' liberated in the water about 

 the hatchery. When order had been restored an attempt was made 

 to recover the lost lobsters, and as a result, over five hundred, which 

 were swimming actively at the surface of the water (fortunately 

 smooth), were picked up by means of scrim nets. 



When we come to examine the behavior of the fifth-stage lobster 

 under natural conditions, we find very diff"erent action. When a 

 number of fifth-stage larvse were cast loose in the open water, it 

 was a most interesting sight to observe them swim for a moment, 



