NOTES ON THE PHOTOPHORES OF SERGESTES PREHEXSILIS 1SATE. 3OI 



Fifth peraeopods One pair. 



Sterilite between bases of fifth peraeopods Six (median). 



Lateral sides of first, second, third, fifth, and sixth 



abdominal tergites Five pairs. 



First to fifth abdominal pleura Five pairs. 



Bases of first to fifth pleopods Five pairs. 



First abdominal sternite Single (median). 



Second abdominal sternite Two ( ,, ) 



Third abdominal sternite One ( ,, ). 



Fourth abdominal sternite One ( ,, ). 



Fifth abdominal sternite One ( ,, ). 



Sixth abdominal sternite Five ( ,, ). 



Uropods Four pairs. 



On two occasions I have had the opportunity of collecting the crustacean 

 myself and of observing the photophores in functional activity, viz., on 

 Marcii 2 and May 31, 1914, at a spot in Suruga Bay about four kilometers 

 off the town of Kambara. On both occasions the capture occurred at 9 

 p. m. Observation then made on the spot showed that, in all the freshly 

 obtained specimens, the photophores emitted dim greenish yellow light in 

 an intermittent way, each time starting suddenly and vanishing with as 

 much promptitude after a longer or shorter period of illumination. 

 Frequently, after dark intervals of varying length, the lighting up of 

 different photophores in the same body occurred one after another in serial 

 succession, beginning with those at the head end and thence progressing 

 posteriorly, to finish up at the tail end. Each single photophore lighted up 

 for nearly a moment only, and as soon as a light disappeared, another 

 appeared a short distance behind in rapid succession, so that there were 

 scarcely ever observed more than one light alive at a time. It took 1-2 

 seconds from start to finish of a single series of illumination of the above 

 sort. At other times, only a limited number of photophores in a certain 

 body region were observed to light up simultaneously, this time the lights 



