192 REFORT OF COMMISSIONERS OF INLAND FISHERIES. 



then, turning head down, disappear for good in the deeper water, — 

 a great contrast to the behavior of the fourth-stage larvse under 

 similar conditions. 



One other set of observations may be mentioned, and these refer 

 to the burrowing instinct of the larval lobsters. When early fourth- 

 stage larvse were transferred to glass dishes, on the bottom of which 

 a layer of sand or gravel and a few broken shells had been spread, 

 the larvae at first gave no heed to these conditions, but for some 

 days continued to swim as persistently as ever. Finally, however 

 (usually within two or three days after the larvse had been placed 

 in the dish), the lobsters began to plough through the sand, especi- 

 ally near the rim of the container, and to construct burrows for 

 themselves beneath shells, stones, or other objects. In the case of 

 the fifth-stage lobsters, on the other hand, when they were intro- 

 duced into the dishes containing sand, gravel, and shells, they com- 

 menced this burrowing at once; and wdien the burrows were com- 

 pleted the lobsters showed a much greater tendency to remain 

 therein than did the fourth-stage larvae under similar conditions. 



The question now arises, what conditions or factors cause these 

 various types of behavior which have been mentioned above: The 

 energetic surface swimming of the fourth-stage larvse, or the bottom- 

 seeking and burrowing habit of the late fourth-stage and the fifth- 

 stage lobsters? Are these reactions to be explained as phototropic 

 reactions, geotropic reactions, response to contact, or do all -three 

 of these, and perhaps still other circumstances, unite in determining 

 the final result? We are not yet prepared to venture an answer to 

 these queries. Some experiments were performed, however, in 

 which the choice between a clear and a sand-covered area was offered 

 to lobsters in the fourth and fifth stages, and methods were intro- 

 duced whereby the lobsters which had gathered in either of these 

 regions could be imprisoned there until they were counted. The 

 results of these tests made it apparent that the early fourth-stage 

 lobsters showed but slight, if any, preference for the sanded area. 

 But when this experiment was repeated with the late fourth-stage 



