ANTHOZOA OF THE WOODS HOIvE REGION. 229 



Among the older students of coelenterates Johnson and Forbes made observations 

 and experiments in connection with the subject, and in turn cite similar observations 

 made by Ehrenberg, Spallanzani, and others, showing no less interest than has been 

 common in later times. 



Macartney proved by experiments that the phenomenon might be aroused by a wide 

 variety of 9,timuH, such as temperature, mechanical disturbance, chemical agents (as 

 alcohol), electricity, etc. Forbes was able to confirm certain of these results, and also 

 proved that in the phenomenon there was no evidence of electrical discharge, and further 

 that no heat was evolved in connection with the emission of light. 



Allman also studied the subject in connection with hydroids. He found the phe- 

 nomenon exhibited by various calyptoblastic hydroids, but not in any known gymno- 

 blastea. Like other observers, he found that various physical and chemical stimuli 

 were needed to evoke displays of light. He was not able to find any phosphorescent 

 secretion in the hydroids, such as had been found in connection with insects and other 

 phosphorescent organisms. 



Among Anthozoa its occurrence has been best known in groups of alcyonaria, 

 especially in species oT Pennalula, Gorgonia, etc., but not unknown in such solitary forms 

 as the actinians. In the latter it has been observed chiefly in the slimy secretion of the 

 ectoderm. 



Reference has already been made to the conflicting theories as to the significance 

 of phosphorescence. A few words must suffice on this point. It was suggested by both 

 Carpenter and Thomson that it might have some importance as.a source of abyssal light, 

 thus affording some means by which the inhabitants of the darkness of great depths 

 might be aided in finding food, evading enemies, etc. But, on the other hand, Mosely 

 has pointed out the inadequacy of such a view. Many facts seem utterly in conflict 

 with the theory. For example, the light of organisms from these depths has been found 

 to be more or less monochromatic, or of only two or three colors. This would suggest 

 that othercolors would be invisible under such light, hence incompatible with the theory. 

 He concludes that colors of deep-sea forms are probably only incidental, or features 

 persisting from earlier conditions when the creatures were inhabitants of shallow waters. 

 And on this and similar grounds he adduces a strong argument as to the comparatively 

 recent migration of many of the abyssal forms into their present habitat. 



Verrill has suggested that phosphorescence might serve as a warning to predaceous 

 fishes that luminous organisms were provided with weapons of defense which it were well 

 to evade. A. Agassiz has pertinently suggested that the well-known cases of Physalia, 

 Cyanea, etc., and their commensals, and the habits of many fishes of feeding constantly 

 in the coral and alcyonarian forests, all went to prove that " they are not in dread of lasso- 

 cells." Among the most brilliantly phosphorescent of our local fauna are ctenophores. 

 But it is well known that these are fed upon by a number of fishes. It may be safely 

 assumed, therefore, that Verrill's suggestion is utterly without significance as an 

 explanation. 



17328°— 14 2 



