164 Mr Matthai, On Reactions 



On Reactions to Stimuli in Corals. By G. Matthai, M.A., 

 Emmanuel College, Cambridge. (Communicated by Professor 

 Stanley Gardiner.) 



[Read 18 February 1918.] 



The following is a brief record of feeding-experiments made on 

 living Astrseid colonies during a short stay at the Carnegie Bio- 

 logical Station at Tortugas (July 16 — Aug. 2) and at the Bermuda 

 Biological Station on Agar's Island (Aug. 20 — Sep. 14) in the 

 summer of 1915, which, though necessarily incomplete as they had 

 to be undertaken in the midst of other work, gave some indication 

 of the nature of reactions to stimuli in the Madreporaria. In order 

 to watch the behaviour of living Corals, colonies of most of the 

 recent species recorded from those localities were kept in aquaria 

 of running sea- water, viz. : 



Mceandra lahyrinthifo7^mis (Linn.), Moeandra strigosa (Dana), 

 McBandra clivosa (Ell. and Sol), Manicina areolata (Linn.), Colpo- 

 phyllia gyrosa (Ell. and Sol), Isophyllia dipsacea (Dana), Isophyllia 

 fragilis (Dana), Dichocoenia Stokesi, Ed. and H., Easrnilia, aspera 

 (Dana), Favia fragum (Esp.), Orhicella cavernosa (Linn.), Orbicella 

 annidaris (Ell. and Sol.), Stephanocoenia intersepta (Esp.), Ocidina 

 diffusa, Lam., Mycetophyllia lamarckana, Ed. and H., Siderastrcea 

 radians (Pallas), Siderastrcea siderea (Ell. and Sol.), Agaricia 

 purpurea, Les., Porites astreoides, Lam., Porites furcata, Lam., 

 Porites clavaria, Lam., Madracis decactis (Ly.), and Acropova 

 muricata (Linn.). 



In Isophyllia dipsacea (Dana), when a particle of meat was 

 placed on the oral disc with contracted mouths, the oral lip 

 was slowly directed towards the particle and the mouth became 

 dilated, to an extent depending on the size of the food-particle. 

 The latter was, in the meantime, slowly moved into the oral open- 

 ing by ciliary action. To facilitate this event, the periphery of the 

 oral disc was drawn over towards the dilated mouth and the disc 

 itself was somewhat depressed, thus deepening the peristomial 

 cavity. During distention of the mouth, the stomodgeum was everted 

 and, consequently, the coelenteric cavity Avith its convolutions of 

 mesenteries became exposed.^ After the food-particle had passed 

 into the coelenteric cavity, it was caught in the mesenterial coils. 

 If the fragment of meat was large, the mouth remained widely open 

 till the former had been reduced in size by the digestive action of 

 the mesenterial filaments. The stomodtEum was subsequently with- 

 drawn and the mouth opening gradually narrowed. But if, before 

 this, the oral lip was touched with a glass needle, it did not contract 

 as it would do instantaneously if no food-particle had previously 



