86 H. NEWTON HARVEY. 



During the past winter at Naples I had an opportunity of 

 examining many luminous forms after exposure to light and these 

 observations, together with previous ones, are collected in this 

 paper. As sources of light the sun (between 10 A.M. and noon), 

 a large carbon arc and a small carbon arc were used. All the 

 light passed through glass and water to absorb the heat. Light 

 from the carbon arcs was condensed by glass lenses. The large 

 arc gave (judging by its inhibition of Cypridina luminescence) 

 at least 10,000 foot-candles while the smaller one, perhaps half 

 of that. Either the whole animal or extracts of luminous 

 material were exposed for the times indicated. 



As to periodicity of luminescence, I have never yet observed 

 an animal which would not luminesce during the daytime, 

 provided it had been kept in the dark for a few hours previously. 

 I have never studied the dinoflagellates but the copepods at 

 Naples (Dec., Jan.), Noctiluca miliaris at Misaki, Japan (July), 

 and Friday Harbor, Washington (Aug.), Balanoglossus minutus at 

 Naples (Dec.), Ptychodera sp. at Bermuda (Dec.), and Pelagia 

 noctilnca at Naples (Dec.) luminesce during the day. 



Other forms in which the whole animal has been exposed to 

 sunlight for the time indicated, and shows no inhibition of lumi- 

 nescence when tested immediately in a dark room are as follows: 

 the ophiurian, Amphiura squamata (Naples, Dec., 15 min.); 

 the annelids, Chsetopterus variopedatus (Woods Hole, July) and 

 Microscolex phosphorea (Naples, Dec., 20 min.); the radiolaria, 

 Thalassicollanucleata, Colozoun inermeand Sphxrozoon punctatum 

 (Naples, Dec. 15 min.); luminous bacteria; luminous fungus 

 (Panus stipticus) (Woods Hole, Aug.) ; pennatulids, Pennatula 

 phosphorea (Naples, Dec.), Cavernularia haberi (Misaki, Japan, 

 July), Ptylosarcus sp. (Friday Harbor, Wash., July); Pyrosoma 

 sp. (Monaco, Jan., 60 min.); Cypridina hilgendorfii (Misaki, 

 Japan, July); the medusae, Mitrocoma cellularia, Phialidium 

 gregarium, Stomatoca atra, and Mquora forskalia (Friday Harbor, 

 Wash., Aug.); the squid, Watasenia scintillans (Japan, May); 

 the fish, Monocentris japonica; and the fire-flies, Luciola parva 

 and viticollis (Japan, July). 



Forms in which a luminous extract has been exposed to the 

 carbon arc and in which no inhibition is to be noted are: Pholas 



