REPORT OF COMMISSIONERS OF INLAND FISHERIES. 205 



containers from many different directions and thus eliminating, to a 

 great degree, tlie directive influence. Still other experiments were 

 performed to ascertain the effects of suddenly blocking the illumina- 

 tion by which the larvie were being stimulated. 



In these eases the ''cut-off" was made by closing the window 

 through which the light entered, thus leaving the larvae in the sub- 

 dued and diffuse light from the room. Inasmuch as the body orien- 

 tation of the larvae to the directive influence of the light is always 

 the same, obviously enough there, could not be very many different 

 varieties of orientation to which the change in the conditions of light 

 could be applied. The resume of these experiments may he pre- 

 sented as follows : 



Resume of Experiments on the Effect of (A) Direct Lighting and (B) 

 Shadowing. — (A) The effect of suddenly submitting the larval lobsters 

 to a light which has a single directive influence is to cause the larvse 

 to orient themselves in such a manner that the longitudinal axis of 

 the body assumes a certain definite relation to the direction of the 

 light rays; and this orientation is a position with the longitudinal 

 axis of the body parallel to the light rays, and with the head turned 

 away from the source of light. (B) The effect of suddenly blocking 

 the light to which the larvae are reacting phototactically, is to cause 

 a new body orientation wherein the head is usually brought to face 

 the direction from which the light had previously come. 



In either of the cases mentioned above, the body orientation is 

 brought about 1)}' a series of motor reflexes s'ome of which Bohn* 

 has described for Homarus vulgaris. 



1. Forward or Backward Rotations or Somersaidts. — These are 

 usually rotations in an arc of few degrees which directly determine 

 a new swimming position. The head is raised or lowered, depending 

 upon the direction from which the light or shadow has been intro- 

 duced. In other cases these rotations may take the form of a varialjle 

 number of complete rotations through 360 degrees, either backward 



