Hadley, Behavior of the American Lobster. 203 



garis), although at first positive in their reaction to Hght, may later 

 undergo certain changes. Herrick (1896) states that larvae of 

 the American lobster react positively to light. Bohn (1905) 

 learned that the reaction of Artemia salina was similar to that of 

 Homarus vulgaris; and the writer has ascertained that the larvae 

 of the green crab, Carcinus granulatus, react sometimes positively 

 and sometimes negatively, and behave very much like the larvae 

 of the lobster. The writer can verify the conclusions pubhshed 

 by Lyon (1906) that the larvae of Palemon may react either posi- 

 tively or negatively to light. 



The results of the small number of investigations which have 

 been made upon the reactions of Crustacea in the larval stages, 

 indicate the desirability of further systematic study of these reac- 

 tions. Pearl (1904) has well pointed out the value of studying 

 the "ontogeny of reaction," and of applying the knowledge there- 

 by gained to the investigation of the more complex forms of 

 response exhibited by adult individuals. Although the writer has 

 not yet had an opportunity to study the behavior of the adult 

 lobster, the present work shows that in the larval stages there are 

 found diverse types of reaction, differing from one moment to 

 another, and depending upon conditions which, even in the nicest 

 experiments, are by no means readily discoverable; and, further- 

 more, that it is only by a systematic study of the reactions through 

 the developmental stages, that many contradictory points can be 

 cleared up, and the more complex behavior of the older animals 

 explained. 



II. BIOLOGY OF the LOBSTER. 



A brief resume of the biology of the lobster will facilitate the 

 understanding of later considerations. The life of the lobster 

 consists of a series of stages or stage-periods, each of which rep- 

 resents the span of life between two successive moults, or castings 

 of its shell. Of these stage-periods, the first four are passed 

 through very rapidly, since the young creature usually moults 

 four times in the first twenty days of its existence. These first 

 few quickly passed stages (called the larval stages because they 

 denote the successive emergence of one from another) include 

 the most important changes in form, color, and manner of behav- 

 ior, that the lobster undergoes. In each successive stage the 

 animal is larger than before. The larvae grow at the time of 



