200 REPORT OF COMMISSIONERS OF INLAND FISHERIES. 



may attempt to ascertain the value of certain light conditions in 

 determining the enaction of these peculiar gymnastics.* 



If larval lobsters of any of the first three stages are submitted to 

 such conditions of light that the stimulus comes from one direction, 

 as from the side, the first fact observable in the reaction is that the 

 larvae undergo a certain body orientation; they turn their heads 

 away from the light and bring the longitudinal axis of the body to 

 lie parallel to the direction of the rays of light. The second fact 

 which may be noticed is, that the larvae, having assumed this body 

 orientation, move in the direction of the light rays, either toward or 

 from the source of illumination. A third fact, which is of maximum 

 importance and which involves the considerations stated above, is 

 that, no matter whether the progressive orientation (motion) of the 

 larvae is towards or away from the source of light, the orientation of 

 the body (head away from the source of light) remains unchanged. 

 To state the matter briefly we may say that, whatever the nature of 

 the progressive orientation of the larvae, the body orientation is at 

 all times, and under all conditions, negative. Bohnf has clearly 

 pointed out this fact for the larvae of the European lobster. In this 

 regard Bohn says: 



En general, les larves de homard se placent dans le sense n^gatif ; meme, dans 

 les premieres heures apres I'eclosion, alors qu'elles se groupent vis-a-vis des 

 lampes leur tete se tourne du cote oppose, et les larves s'approchent de la lumiere 

 en regardant I'obscurite, c'est-a-dire en reculant. Ainsi, apres I'eclosion, 1'- 

 orientation a lieu dans le sens negatif, mais le deplacement se fait dans le sens 

 positif. Dans la suite, si le sens de I'orientation reste le meme. le.sens du deplace- 

 ment pent changer. 



Quite recently LyonJ has recorded a similar observation for cer- 

 tain larval stages of Palemon. The condition of affairs here noted is 



*Many of the observations which follow were made previous to the writer's knowledge of 

 the excellent work of Georges Bohn, of Paris, along similar Unes, but involving observations 

 upon the larvie of the European lobster, Homarus vulgaris. The writer would acknowledge his 

 great indebtedness to this investigator, whose work has proved suggestive in the highest degree; 

 and whose observations on the mechanics of beha^^or the writer has been able, in the majority 

 of instances, to verify and add to. 



timpulsions Motrices D'Origine Oculaire chez les Crustaces. Institut General Psychologique, 

 Exlrait du Bulletin no 6-5 e annee. 1905 



JBiol. BuUetin. 1906, Vol. XII, p. 23. 



