NOVEMBEK 5, 1915] 



SCIENCE 



661 



Friday, August 6 

 Morning Sessioii, Demonstrations 

 In charge of F. W. Weymouth 

 liiving Ova of Bat in Serum, J. A. Long, Uni- 

 versity of California. 



Papers: Marine Zoology 

 F. M. McFaeland, Stanford University, presiding 



The Occurrence and Possiile Causes of Periodic 



Vertical Movements of Aquatic Organisms: C. 



O. E STEELY, Occidental College, Los Angeles, 



California. 



It is well known tliat many aquatic organisms, 

 particularly those of the plankton, are more 

 abundant at or near the surface by day than by 

 night. This is because they ascend from deeper 

 water in the early part of the night and descend 

 from the surface later. 



In order to understand the fundamental causes 

 of this phenomenon it is necessary to have accu- 

 rate knowledge of the field conditions under which 

 collections are made, particularly of the tempera- 

 ture and salinity of the water and of the light in- 

 tensity as represented by the time of day at least. 

 It is highly important that field observations be 

 supplemented by laboratory experiment to deter- 

 mine to what sorts and degrees of stimuli the or- 

 ganisms respond. Furthermore, each species must 

 be studied by itself. 



The explanation of the diurnal movement that 

 at present is most satisfactory is the one based on 

 responses to different factors in the environment, 

 but our knowledge in this respect is very incom- 

 plete. The "mechanical explanation" which 

 takes into account mainly the changes in viscosity 

 of the water does not satisfy. The suggestion 

 that the alternating rise and fall is due to meta- 

 bolic rhythms has received so little attention that 

 its worth is not apparent. 



Some Physiological Characters of Marine Animals 

 from Different Depths: V. E. Shelpord, Uni- 

 versity of Illinois, Urbana. 



Field Study of Animal Behavior as contrasted 

 with Laboratory Study: Ellis L. Michael, 

 Scripps Institute, La Jolla, California. 

 The object of this paper is to emphasize the 

 necessity of employing two essentially distinct but 

 mutually helpful methods of research in any 

 strictly scientific study of animal behavior. All 

 biologists readily admit that an important func- 

 tion of the well-known laboratory method is that 



of analyzing the mechanism involved in an organ- 

 ism's response. Few, however, seem to realize 

 that this method is incapable of revealing how 

 any particular species is related to its environ- 

 mental complex. 



Yet, the minute a definite answer to such a ques- 

 tion is sought, a little thought clearly shows that 

 recourse must be had to some method of field ob- 

 servation. For instance, could any amount of 

 laboratory experimenting reveal the fact that 

 Sagitta iipunctata is more abundant between 15 

 and 25 fathoms than at any other depth, or that 

 it increases in abundance as the distance from the 

 coast decreases? 



In order to demonstrate the indispensability of a 

 field method three aspects of the behavior of 8. 

 hipunctata are illustrated in some detail. First, 

 the variation in abundance at all depths at differ- 

 ent times of day is considered, showing how the 

 species migrates vertically. Second, the fact that 

 it accumulates in all depths in greatest numbers 

 when the temperature lies between 13° and 16° 0. 

 is revealed. Third, data are presented showing 

 that the species is more abundant, on the surface 

 at least, when the salinity lies between 33.55 and 

 33.70. 



Finally, the question of the interpretation of the 

 results is discussed. Attention is called to the fact 

 that an adequate interpretation necessitates re- 

 course to the laboratory method. Obviously the 

 field method can not, except by interference, as- 

 certain the nature of response involved, i. e., as 

 to whether the demonstrated relations are due to a 

 tropism, a taxis, a metabolic reaction, or to a 

 direct physical effect of changes in viscosity and 

 a specific gravity. 



The Influence of Chance on the Number of Or- 

 ganisms Collected in Planlcton Nets: George F. 

 McEwen, Scripps Institute for Biological Ee- 

 search. La Jolla, California. 

 Measurements of a number of hydrographic ele- 

 ments and the corresponding abundance, or num- 

 ber of a species per unit volume of water in the 

 ocean supply the data for determining the way in 

 which the distribution of the species is related to 

 these elements. 



Practically, the distribution of the smaller or- 

 ganisms must be inferred from the number of 

 each species collected per haul made with a plank- 

 ton net. A plankton net filters rather variable 

 fraction of the water that would pass through the 

 net rim, if unobstructed; also the estimate of the 

 distance hauled is usually subject to accidental 

 errors of importance. 



