302 CLASSIFIED RESUME OF ORGANISMS OBSERVED 



— with copepods of course as the dominant visible organ- 

 ism — ^was not swirhng in the path of the beam. 



Usually the individual animals were indistinct, forming 

 only an ever-shifting, unobtrusive atmosphere of tiny 

 silvery motes through which larger organisms were ob- 

 served. But whenever, by an effort of concentration, I 

 focused on a small copepod group close to the glass, I 

 could segregate one or two large individuals and catch 

 momentary clear impressions of color and activity. Thus 

 occasionally I saw every detail of a brilliant blue copepod, 

 its cephalothorax almost as slender as its abdomen, and the 

 caudal rami fully three times its total length, and recog- 

 nized it as a species, so far unidentified, which is fairly 

 common in our trawling nets. At lower levels the large 

 scarlet form with purple eggs, HeteromalUa dubia, stood 

 out in similar manner. The plankton in the beam always 

 tended to break up and reflect the rays back towards the 

 sphere in faint opalescent flashes, which resembled the 

 sparks of truly luminous animals. But occasionally a flash 

 of brilliant iridescence was seen in the beam, and I am sure 

 I saw simultaneously the broad, flat oval of a male Sap- 

 phirina. This genus is the commonest of the larger forms 

 of copepods in our nets. 



Luminescence is rare among the copepods. One indica- 

 tion is that luminous individuals were reported only three 

 times. Another, and this is the more important of the two, 

 is the following: Although, as has been said, large num- 

 bers were visible every time the beam was switched on, yet 

 the sparks outside of its path were few in number com- 



