148 foiiriial of Comparative Neurology and PsycJiology. 



flexes of the legs, such as the gustatory and swimming move- 

 ments, appear at this early stage. 



Reactions to Stininli. — It is rather surprising to find that 

 before the time of hatching the embryos are extremely sensitive 

 to mechanical stimuli applied to the external surface of the 

 "vicarious chorion." If the surface of the "vicarious chorion" 

 be touched very gently with a needle the embryo stops all 

 movement at once, draws the legs back as far as possible into 

 cephalothorax and strongly flexes the abdomen, so as to make 

 practically a right angle between it and cephalothorax. These 

 positions are maintained as long as the stimulus is continued. 

 In a short time after the stimulation ceases the abdomen is ex- 

 tended, and the respiratory and leg movements begin again. 



A B 



Fig. f. — Diagrams showing appearance of Limulus embryo immediately 

 after hatching. A. Haemal side. B. Neural side. (After KiNGSLEY). 



This is the same reaction as that given in response to 

 mechanical stimuli after hatching. It is somewhat remarkable 

 that the organism should respond in the same way to the press- 

 ure of a needle point when in one case this pressure has first to 

 be transmitted by the surrounding fluid to the embryo, and in 

 the other case the needle point touches the surface of the body 

 directly. 



Hatching. — The behavior at the time of leaving the "vicari- 

 ous chorion" I have not been able to observe. In the material 

 which I had all the hatching occured during the night. 



