554 



SCIENCE 



[N. S. Vol. XXVI. No. 669 



■what the water contained over at least the 

 area traversed — whereas we now know that the 

 Zoeas were confined to, at most, the latter 

 half of the traverse and may have been even 

 more restricted. Under these circumstances, 

 an observation made solely in the water tra- 

 versed during the first seven minutes would 

 have given a very different result from that 

 actually obtained; or, to put it another way, 

 had two expeditions taken samples that eve- 

 ning at what might well be considered as the 

 same station, but a few hundred yards apart, 

 they might have arrived at very different con- 

 clusions as to the constitution of the plank- 

 ton in that part of the ocean. 



It is interesting to note that enormous 

 numbers of Oilcopleura " houses " covered with 

 diatoms were present in some of the gather* 

 ings; and the abundance of the diatom 

 TTialassiosvra N ordenskioldii was phenomenal. 

 We have some reason to think that there has 

 been an exceptional flow of cold water from 

 the north into the Irish Sea this spring and 

 that may account for the presence of this 

 northern diatom which has not been found in 

 our region before. 



As an example of two surface nets hauled 

 together which gave much the same quantity 

 of plankton, but where the gatherings dif- 

 fered widely in their nature, I may give the 

 details ,of April 13. [Slide shown and de- 

 tails explained.] 



The bearing of such observations as these 

 upon some recent speculations as to the fish- 

 population of the sea, and even as to the 

 amounts of food-matters present in the waters 

 of large areas, is obvious. Nothing in the 

 economics of the sea could be more important 

 than such speculations in regard to what I 

 have proposed should be called the " hylo- 

 kinesis " of the ocean, if we could be certain 

 that our conclusions are correct, or even that 

 they are reasonably close approximations. 



It is possible to obtain a great deal of in- 

 teresting information in regard to the hylo- 

 kinesis of the sea without attempting a 

 numerical accuracy which is not yet attain- 

 able. The details of measurement of catches 

 and of computation of organisms become use- 

 less and the exact figures are non-significant. 



if the hauls from which they are derived are 

 not really comparable with one another and 

 the samples obtained are not adequately repre- 

 sentative of nature. If the stations are so 

 far apart and the dates are so distant that 

 the samples represent little more than them- 

 selves, if the observations are liable to be 

 affected by any accidental factor which does 

 not apply to the entire area, then the results 

 may be so erroneous as to be useless — or worse 

 than useless, since they may lead to deceptive 

 conclusions. 



My view in brief is: (1) That we must in- 

 vestigate our methods before we attempt to 

 investigate nature on a large scale, (2) that 

 we must find out much about our gatherings 

 of organisms before we can consider them as 

 adequate samples ; and (3) that we must make 

 an intensive study of small areas before we 

 draw conclusions in regard to relatively large 

 regions such as the North Sea or the Atlantic 

 Ocean. 



W. A. Heedman 



A SIMPLE ELECTRIC THERMOEEGULATOR 



The advantage of electricity over gas for 

 heating paraffin baths, incubators, culture 

 chambers, etc., in laboratories is well known. 

 Electric thermoregulators for use in connec- 

 tion with such apparatus have appeared from 

 time to time ; but, as far as I know them, they 

 are all more or less compUcated or expensive. 



The electric heating coil and regulator de- 

 vised by Professor E. L. Mark' and used with 

 success in the laboratories of the museum of 

 comparative zoology at Harvard University 

 ever since, costs between $25 and $30 for each 

 bath. The expense of this device excludes its 

 use in many laboratories, especially those in 

 which quite a number are desired for indi- 

 vidual use. 



It was for the purpose of heating a small 

 paraffin bath with a sixteen-candle power in- 

 candescent lamp that I first devised an electric 

 thermoregulator. Later modifications of this 

 piece of apparatus resulted in two forms, a 

 mercury regulator and a glycerin or air regu- 



»]VIark, E. L., "A Paraffine Bath Heated by 

 Electricity," Amer. Nat., 37 (434): 115-119, 3 

 figs., Febrxiary, 1903. 



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