222 A. T. CAMERON AND C. H. o'DONOGHUE. 







tion became more active. After 45 minutes activity had nearly 

 ceased. The " darkness " reflex was present, but not marked. It 

 was shown by sudden spasmodic movements of legs and chelae. 

 After a further 15 minutes a "light" reaction was doubtfully 

 present; the "darkness" reaction was marked. The latter slowly 

 decreased. After 70 minutes' immersion the crab scarcely re- 

 sponded to any stimulus. It was then removed to fresh sea-water 

 and slowly recovered. 



Camphor (i: 16000). A smaller specimen showed a marked 

 " darkness " reaction seven minutes after immersion. There was 

 a general " flick " of legs and chel'se, but no coordination. ;< Light " 

 produced no effect. After nine minutes' immersion the reaction 

 was no longer given ; the animal scarcely responded to any stimu- 

 lus. Transferred to fresh sea-water, it did not recover. 



Menthol (saturated solution). A similarly sized small speci- 

 men showed the " darkness " reaction after 12 minutes' immersion. 

 The " light " response became evident after 22 minutes, and after 

 30 minutes both " light " and " darkness " responses were distinct. 

 The animal commenced to struggle violently, shed both chelae and 

 three legs, and thereafter became scarcely responsive to any stim- 

 ulus and (35 minutes) was evidently moribund. 



(C) Cancer productus. A fairly large crab found on the sea- 

 bottom near the station wharf. Specimens placed in fresh sea- 

 water under experimental conditions gave no noticeable response 

 to changes of illumination. " Darkness " produced very occasion- 

 ally slight twitches, shown chiefly by movements of the claws. 



Benzene (1:1500). A medium-sized specimen (93 grams) 

 was immersed. In six minutes a " darkness " reaction was evi- 

 dent. In 18 minutes both " light " and " darkness " responses were 

 marked. The response consisted of spasmodic contractions of the 

 legs and claws, so that the whole crab was raised. When placed 

 on its back and tested, all the limbs suddenly contracted. The 

 third maxilliped shut and the abdomen was brought up tightly 

 against the carapace. After 32 minutes "light" and "darkness" 

 responses were still evident, but slight, and on touching the animal 

 little response was evoked. After 38 minutes the animal was 

 apparently dead. It was removed to fresh sea-water, but did not 

 recover. 



