128 DR. G. H. FOWLER — BISCAYAN PLANKTON : 



taken within two hours and a quarter ; in this case it is just worth notice that they 

 were morning hauls after a night of very heavy rain and thunder. 



In this connection it would be worth the while of future observers to consider whether 

 the mere presence of a ship hove-to does not, after a time, concentrate certain species : 

 the offal of a ship is very considerable, and means a sudden enhancement of the food- 

 supply, which might perhaps account for some of the apparent variations in population. 

 The hauls 31 h, 34 a, h, c were all made after a considerable period of laying-to. 



It may be argued that the proportional catches of larvae and adults confirm the idea 

 that adult Schizopods can see and avoid (or swim out of) the net in daylight, and hence 

 are caught more plentifully by night, while the larvse, moving more slowly, would 

 naturally be caught more abundantly in the day than adults. But if this were the sole 

 explanation, larvse ought to have been captured equally i)lentifu]ly by day and by night, 

 whereas they were absolutely (not relatively) taken in far greater numbers in daylight. 

 Besides, as Messrs. Holt and Tattersall point out, S. Snhmli must be a feeble 

 swimmer, if only in consequence of the length of some appendages. 



The idea that even large Schizopods can (except possibly at the surface) see a net and 

 avoid it is not easy to grasp. Tliose of us who have tried to pick up white plates, or 

 chalk eggs, in even a few feet of water, know how rapidly the light diminishes in those 

 few feet. At 100 fathoms the experiments of Fol and Sarasin do not seem to 

 demonstrate the presence of more than a twilight of actinic rays ; the red and yellow 

 rays are stopped in a comparatively short passage through sea-water. It may be urged, 

 and is quite possible, that the eyes of Schizopoda can appreciate rays invisible to our 

 eyes : Moseley suggested many years ago that the large eyes of some abyssal forms 

 might " see " the heat-rays given off by other organisms. But if ordinary light and 

 vision can help a Schizojiod to escape capture, surely a brilliantly phosphorescent net by 

 night must be a more conspicuous object * than the same net used by day at any depth 

 beyond 25 fathoms ; and, further, in such cases as the three plentiful Schizopods tabled 

 above which extend to 100 fathoms, the captures at that depth during daylight should 

 approximate to those at the same depth during night, the light there being so small, and 

 the phosphorescence presumably as brilliant as at the surface ; at least, more should 

 be captured at 76 than at 50 fathoms, more at 100 than 75 fathoms, yet this is not 

 the case (compare tables, p. 127, adults). 



It seems to me to be more probable that strong swimmers, such as Araphipoda and 

 Schizopoda, are actually caught in the ordinary slowly-moving tow-net, but in daylight 

 make for the brighter end of it — the mouth — exactly as a bee in a room makes for the 

 window. It is in the experience of every tovv-netter that a wide-meshed net t, whicli 

 allows of a faster current through it, catches more of such organisms than a fine-meshed 

 net, in which the current is reduced. But I doubt if t.liis accounts for all the facts; it 



* Mr. Holt tells me that the reason that bright moonlight is good for mackerel-fishing is alleged to be that the 

 phosphorescent nets are less conspicuous in the bright light. 



t We failed to tow-net advanced lobster larvae at Plymouth till a wide-meshed net was used at a comparatively 

 rapid pace. 



