260 HOVEY JORDAN 



ing marine fishes Mustelus canis, Anguilla chryspa, Stenotomus chry- 

 sops, Tautogolabrus adspersus, Tautoga onitis, Chilomycterus schoepfi, 

 Opsanus tau and Microgradus tomcod possess integuments which 

 are unresponsive to photic stimulation. He concludes, therefore, that 

 cutaneous photosensitivity may be a characteristic of fresh-water 

 fishes, as phosphorescence is of certain marine organisms. 



But in the course of certain experiments upon the hamlet (Epineph- 

 elus striatus), I discovered, contrary to this theory, that both nor- 

 mal and blinded fishes are negatively phototropic. Their reactions 

 closely resembled those of the fresh-water fishes which have already 

 been described by several authors. Eigenmann ('00) has shown that 

 the blind fish Amblyopsis is negatively phototropic; Parker ('05) found 

 the common brook lamprey, Ammocoetes, to be negatively phototropic 

 and also photodynamic ; and Payne ('07), who studied Amblyopsis, states 

 that this fish is negatively phototropic and photodynamic regardless 

 of the direction of the rays of light and also that its sensitivity to light 

 decreases with age. 



Fundulus, however, is reported to be an exception to the theory of 

 universal cutaneous photosensitivity among the non-marine fishes, 

 since Long (see Parker '05) and Parker ('09, p. 77) were unable to stimu- 

 late its skin with light. It might, however, be urged in explanation of 

 this apparent exception that Fundulus is adapted to life in salt water 

 (as well as in fresh) and simply shares with other marine fishes their 

 characteristic insensitivity to light. 



It is therefore of considerable interest that at length a marine fish 

 with no known proclivities for life in fresh water has been found in 

 which there is a marked photic sensitivity. Though only a single case, 

 this may well cause one to hesitate in adopting the view that there is 

 any fundamental and constant difference in this respect between the 

 fishes of salt and of fresh water. It will perhaps also suggest that 

 photosensitivity of the skin of lower verebrates is a capacity which has 

 been independently acquired (or retained?) by remotely related forms. 



B. Purpose of experiments 



In view of the interest attaching to the question and the importance 

 of a critical examination of these responses, further experiments were 

 at once undertaken.' They aimed, first, to determine more carefully 

 the positive or negative character of the phototropism observed; sec- 

 ondly, to discover any evidence of photodynamic responses; and, 



