RETINAL REFLEXES OF NARCOTIZED ANIMALS. 221 



2. Echinodcnnata. EcJiinoidca. Strongylocentrotus drobachien- 

 sis. Sea-urchins found on the under surface of the float on the 

 station wharf. 



Benzene (i :2OOo) produced an immediate immobility, and light 

 changes ceased to produce any movement of spines. The animal 

 was completely narcotized in six minutes. 



Camphor (resuhlimed, i : 16000) produced the same result, and 

 was fatal in less than eleven minutes. 



Menthol (half-saturated) produced quiescence in three minutes. 

 Light changes produced no discernible results. 



30. ArtJiropoda. Crustacea. Dccapoda. 



(A} Hemigrapsus nitdits. A shore crab found plentifully be- 

 tween tides under rocks at the station. When specimens were 

 placed in sea-water under the experimental conditions, " dark- 

 ness " produced a sudden stoppage of movement, and an occasional 

 " flick," very slight. 



Benzene (1:1500) produced narcosis in one or two minutes. 

 Before this was complete the crab reacted to " light " by general 

 activity movement of chelae and legs, and sometimes of the eye- 

 stalk. " Darkness " produced no effect. 



Benzene (i : 3000). Two animals gave a " darkness " response, 

 definite, but not much greater than normal, after one minute. 

 After five minutes even touching them produced no response, and 

 after ten minutes narcosis was complete. 



Phenol (i : 2000) was fatal to these crabs in from 30 to 40 min- 

 utes. Some minutes previously to death both " light " and " dark- 

 ness " produced marked reflexes. 



Camphor (i : 16000) produced no effect. The crabs were nor- 

 mal after 6 hours' immersion. The resublimed camphor (i: 

 16000) produced in a somewhat small specimen (7 grams) a 

 "darkness" response in 10 minutes, and in a larger one in 40 

 minutes. In 45 minutes both gave marked responses, which con- 

 tinued for some time. After 15 hours' immersion slight responses 

 could be elicited. It was doubtful that these were greater than 

 normal. The animals were otherwise normal at that period. 



(B) Epialtns productus. A "kelp crab," a somewhat larger 

 species, found amongst eel-grass near the station at low tide. 



Benzene (1:2000). A large specimen immersed in this solu- 



