Hadley, Behavior of the American Lobster. 237 



fourteenth day. In this particular instance, twenty larvae were 

 transferred to the glass jar and placed in the dark box. The 

 resulting reactions to the colored lights were as follows: 



Color. Positive. Nec^tive. 



Red 16 4 



Orange 1 6 4 



Green 



Blue 13 7 



White 9 II 



Day o 20 



It may be observed in the account of the last three experiments 

 how the general reaction of the third-stage larvae has gradually 

 changed from negative to positive; and how it requires an increas- 

 ingly greater intensity of light to determine a negative response 

 in the larvae which are approaching the fourth stage. In the next 

 case the culmination of this gradual change is reached, since the 

 third-stage larvas almost uniformly manifest a positive reaction 

 which is as definite as that of the newly-hatched larvae. 



Case 4. — July 30, 2 p.m. Thirty fourteenth-day, third-stage 

 larvae secured from a group in which nearly all had entered the 

 fourth stage, were transferred from the hatching bag to the glass 

 jar and placed in the dark box under the influence of colored 

 lights: 



Color. Positive. Negative. 



Red 30 o 



Orange 30 o 



Green 30 o 



Blue 30 o 



White 28 2 



Day 23 7 



It is here observed that, when as indicated above, the jar was 

 removed from the dark box and placed on the west table in day- 

 light, only seven larvae became negative. All the others remained 

 positive, even in this light of great intensity. This case represents 

 the strongest and most definite maintenance of the positive reac- 

 tion in late third-stage larvae ever observed by the writer. These 

 larvae moulted into the fourth stage very soon after the above 

 observations were made. 



Case 5 — In the following test other members of the group of 

 larvae used in the previous case were employed. The aim was 

 to learn whether or not the photopathic reaction in these larvae 

 was in agreement with the phototactic reaction described in Case 



