286 



DE. G. H. I'OWLEE— BlSCAlAN PLANKTOK : 



Secondly, of tlic 235 specimens actually captured, no less than 65 per cent, were taken 

 in two hauls on a single night (30 I, 31 b, 50 fms.), forming a veritable swarm. The 

 remaining epiplanlcton specimens were scattered fairly evenly over the night hauls — in 

 5 out of 7 night hauls at 75 fathoms, in 6 out of 8 night hauls at 100 fathoms. Thirdly, 

 the steady occurrences between 1000 and 200 fathoms seem to point to the species being 

 mesoplanktouic, although it was missed altogether between 200 and 100 fathoms ; but, 

 except for the two hauls ah*eady mentioned, it was nowhere so plentiful nor so regularly 

 captiu'ed in the epiplankton as that one should expect to find numerous corpses in deep 

 water. 



In short, daphnoldes was in the epiplankton practically by night only, was missed 

 between 250 and 100 fathoms, and reappeared between 1000 and 300 fathoms. It seems 

 almost inconceivable that the upper specimens at night retired to 300 fatlioms by day 

 and returned iii the evenmg : muscular effort seems inadequate, and we do not know to 

 what extent and by what methods a Crustacean can alter its sj)ecific gravity. A possible 

 clue is given by the fact that of the 235 specimens captured all were at the oldest stage 

 except one single one : this implies that breeding had not taken place in that water for 

 some time past ; it is conceivable that a mass of the specimens had risen to breed, in the 

 way suggested by Chun and others for certain groups. But the species was nowhere 

 plentiful in the mesoplanktou, and may simply have been missed in the hauls between 

 250 and 100 fathoms, in the ordinary run of chances, since each havil only filtered 

 theoretically 11-12 cubic feet of water. 



At 



Between 



CONCHCECIA ELEGANS, Sars. 



per cent, of 13 hauls, with 0-00 " 



out of 



12 

 13 

 10 

 17 



7 

 3 

 o 



o 

 O 



3 



4 

 5 



0-75 



6-76 



36-40 



4-64 



0-85 1 

 2-33 

 100 

 0-33 ) 

 0-33 j 

 0-30 

 0-08 J 



average 



specimens 



per hour 



haul. 



specimens per 



100 fathom 



haul. 



Of the 582 specimens actually captured in the epiplankton (or 510 when treated with 

 the time-factors) only two specimens were taken in daylight. This seems to sliow that 

 the species as a whole rises by night and sinks by day. But it does not appear that it 

 extends to such depths as do some species ; judged by the " average specimens per 100 

 fathom haul " of the foregoing table, one would not infer that it was living deeper than 

 300 fathoms, and 250 fathoms is probably nearer the mark. 



As with daplmoldes, the majority of the specimens came from two hauls at the same 

 depth on one night : but they were two nights later than the big hauls of dajphnoidea, 



