Mat 27, 1910] 



SCIENCE 



835 



executive committees of both branches were elected 

 to membership in the Central Branch: J. T. Pat- 

 terson, University of Texas; Robert T. Young, 

 University of North Dakota; John W. Scott, 

 Kansas City High School; F. D. Barker, Univer- 

 sity of Nebraska; Albert Kuntz, University of 

 Iowa; Chancey Juday, Wisconsin Geological and 

 Natural History Survey; H. W. Norris, Grinnell 

 College. 



The following are titles and abstracts of papers 

 presented at the meeting: 



Some Personal Peculiarities of Lakes (president's 

 address) : Edw. A. Bebge, University of Wis- 

 consin. 



The paper dealt with certain unusual, but regu- 

 larly recurrent phenomena in the temperature, 

 dissolved gases and carbonates of several inland 

 lakes, and with the biological meaning of such 

 phenomena. On the annual rhythm of physico- 

 chemical changes in a lake, produced by the march 

 of the seasons, there is superimposed another 

 annual series of similar changes, due to biological 

 causes. These last are in large measure regular 

 and determined by general laws; but in part, and 

 especially in their details, are peculiar and " per- 

 sonal " to the several lakes. They result from the 

 establishment of habitual interactions between the 

 members of the plankton and between plankton 

 and environment. 



Inland lakes contain a complex and practically 

 closed assemblage of plants and animals, which 

 have lived together for centuries, in an environ- 

 ment substantially unaltered from year to year 

 and whose exchanges with the outer world are 

 minimal. Thus the lake with its plankton has 

 come to be a sort of organism of a higher order, 

 showing definite and regular internal changes and 

 reactions not unlike those of an organism — 

 changes not so definitely expressed or so defi- 

 nitely dependent on biological causes in any 

 other assemblages of organisms. In certain lakes 

 we find habitual reactions, unexpected a 'priori, 

 and in this respect not unlike reactions of higher 

 organisms. 



Inland lakes, therefore, offer to the student 

 definite and varied ecological problems of much 

 interest and complexity. These concern the rela- 

 tion to each other of members of the plankton, 

 the effects of plankton on ennronment and the 

 resulting influence on plankton of environmental 

 changes. Such problems are by no means wholly 

 general, to be solved by the study of a single lake, 

 but they ofi'er many features which are special 

 and personal to individual lakes. 



Feeding Reactions of the Rose Coral {Isophyllia) : 

 F. W. Cakpextee, University of Illinois. 

 When the rose coral polyp is stimulated by 

 meat juice the oral disk is drawn downward by 

 the contraction of the retractor muscles of the 

 mesenteries, and the margin of the oral surface 

 is folded inward over the disk by the action of 

 a well-developed sphincter muscle. Meanwhile, 

 the stomodseum is everted, and the mesenterial 

 filaments are extruded both through the mouth 

 and through temporary apertures in the oral disk. 

 Carmine particles dropped on the oral surface of 

 an expanded polyp are transferred by ciliary 

 action to the periphery. When the carmine grama 

 have previously been soaked in meat juice the- 

 cilia usually continue to beat in an outward 

 direction; occasionally, however, they reverse 

 their effective strokes. The tentacles react quickly 

 to contact stimulation, and afiix the touching 

 object to their knob-like distal ends, which are 

 heavily loaded with nematocysts. 



In normal feeding, which occurs after dark, 

 small organisms in the plankton are aSixed by 

 the tentacles, the oral disk sinks, and the mar- 

 ginal zone of the polyp folds inward until it com- 

 pletely roofs over the tentacles and the depressed 

 oral disk. Into the superficial chamber thus 

 formed the stomodseum and mesenterial filaments 

 project, and here the mesenterial filaments, which 

 are the digestive organs of the polyp, probably 

 digest and ingest or absorb the captured plankton, 

 little of which finds its way into the reduced 

 gastro-coelomio cavity. Extra-coelenteric digestion 

 appears, therefore, to take place in rose coral 

 polyps. 



The Factors which Control the Leaping of the 



Pacific Salmon: Henet B. Waed, University of 



Illinois. 



Open water jumping was observed best among 

 salmon swimming about in a pound net or trap. 

 The same fish does not execute a series of leaps, 

 but only a single jump. Features in the position 

 and movements of body and fins show that it is- 

 neither an effort to escape capture nor prepara- 

 tion for the ascent of the stream later. It must 

 be regarded as a type of play which, however, 

 finds expression only as the reproductive period 

 approaches. It occurs first at the time when the 

 reproductive organs are entering upon their final 

 growth period. 



Jumping at falls manifests in several particu- 

 lars of position and movements of body and fins 

 a definite relation to the purpose of surmounting 

 the obstacle. In a large per cent, of cases the 



