LUMINESCENCE 



573 



luminescent glands and the secretion of more material. At low frequencies 

 of stimulation the response is quite local, whereas rapid and prolonged 

 stimulation leads to transmission of excitation through the nerve cord and 

 a more widespread response from all luminescent regions of the body. 

 Moreover, transmission takes place with greater facility posteriorly than 

 anteriorly through the nerve cord. 



Still uncertain is the method of regulation obtaining in Pyrosoma. 





rrrrrmr^r^t r r 



r 



r 



T 



(a). 



Fig. 13.27 (a). Photo-electric Recording of Luminescent Flashes of 



Acholoe aster kola 



Flashing induced by a pair of electrical shocks (pips on lower line). Flashes shown as 

 downward deflexions of middle trace. Time scale above, 1/sec. 



Fig. 13.27 (b). Record of Luminescent RESPONSEs]oF^C7z<z<?/ 1 0/?/ 1 m/.s' variopedatus, 

 Recorded by Multiplier Photocell and Galvanometer 



Stimuli (condenser shocks) indicated by arrows. Upward inflexion indicates luminous 

 response. Time scale above, 1/min. 1, base line. 



The fact that light appears only on stimulation and then spreads over the 

 colony is additional evidence that the animal produces its own photogenic 

 material. Panceri implicated muscular tissue and presumably an associated 

 nerve supply, extending from one individual to another, in the transmission 

 of excitation, but there is still no clear idea how such transmission occurs 

 and how lighting is regulated. 



Some fragmentary observations on luminescence in fishes are available. 

 In the shark Etmopterus luminescence follows tactile stimulation after a 



