474 



SCIENCE 



[N. S. Vol. XXXI. No. 795 



rise in temperature; (7) the geographical distri- 

 bution of typhoid cases over the city was largely 

 independent of areas known as " unsanitary " and 

 as " fly centers." 



The conclusions drawn from these results point 

 toward a more fundamental factor than the house 

 fly in the spread of enteric diseases. Further- 

 more, judging from the constant relationship 

 which the temperature curve maintained through 

 the experiment, it is not unnatural to suppose 

 that therein lies the solution of the problem; but 

 whether the influence of temperature is real or 

 only apparent, direct or indirect, remains yet to 

 be determined. 



The Leaping of the Pacific Salmon: Henby B. 



Wabd, University of Illinois. 



Observations made, chiefly in southeastern 

 Alaska, on the red and humpback salmon indicate 

 that the fish do not choose a particular point of 

 attack in endeavoring to surmount a fall. The 

 height and length of the jump were very variable 

 and on the whole there appeared to be a remark- 

 able lack of accuracy as well as of definiteness in 

 the movement. This apparent aimlessness of the 

 leaping may be the result of a fairly precise re- 

 sponse to definite stimuli in the water currents 

 which in the small whirlpools below the falls are 

 subject to constant and unexpected changes. 

 When endeavoring to surmount the falls the fish 

 sail through the air with body rigid and fins 

 spread tense, while at the instant when the mo- 

 mentum of the jump is lost one notes a series of 

 rapid and powerful vibrations of the tail; these 

 are made regardless of the success of the jump 

 or of the position of the fish in air or in water. 

 If the fish reaches solid water at the crest of the 

 fall, they insure the maintenance of the vantage 

 thus gained. 



The open water jumping is of a distinct type, 

 since the body leaves the water sidewise instead 

 of in a vertical position, the musculature is some- 

 what relaxed and the fins are partly folded back- 

 wards, while finally there is no movement of the 

 tail at the close of the jump. The purpose of this 

 jump is not clear. 



Direction of Locomotion of the Starfish {Asterias 

 forbesii) : L. J. Cole, Yale University. 

 It was shown that in the absence of directive 

 stimuli, although starfishes might move with any 

 ray in advance, in a large number of trials it was 

 most often the one lying next to the left of the 

 madreporic plate which went ahead. This may 

 perhaps then be considered the physiological an- 



terior of the animal. Attention was called to the 

 fact that in the bilateral echinoids, the spatan- 

 goids, it is similarly the ambulacral area to the 

 left of the madreporite which is anterior. 

 Reactions of Echinoderms to Light : E,. P. CowLES, 



Johns Hopkins University. (Presented by 



title.) 



A review of the literature dealing with the 

 reaction of starfishes to light shows there is a 

 general belief that these animals depend for their 

 responses to light upon the eye spots situated at 

 the tips of the rays. Some authors even state 

 that certain starfish do not react to light when 

 these organs are removed. 



While experimenting with the starfish, Eohin- 

 aster crassispina, the writer found that the eye 

 spots may be removed and that the creature may 

 still react to differences in the intensity of the 

 light. The tips of the rays of several echinasters 

 were amputated and these starfish were then 

 tested in a rectangular glass dish lined with dead 

 black paper and filled with sea water. The dish 

 was placed in a black-lined box with a single 

 opening at one end through which bright day- 

 light was allowed to enter. When a series of 

 tests were made the starfish was placed in the 

 dish, care being taken to vary the manner of 

 handling and also to vary the position of the 

 rays with reference to the source of light. In the 

 majority of tests the echinasters moved to the 

 lighter end of the dish, although the reaction was 

 somewhat slower than with normal individuals. 

 Reactions of Amceha to Light: S. 0. Mast, 



Goueher College, Baltimore. 



If direct sunlight is flashed on an active speci- 

 men of Amteba proteiis all movement stops imme- 

 diately. The pseudopods remain just as they are, 

 without contracting, until after the lapse of a few 

 moments, when new ones are thrown out, usually 

 at the posterior end. Then the old ones gradually 

 disappear. This occurs in the blue of the solar 

 spectrum nearly as definitely as in white light. 

 Green is much less eflFective; violet, yellow and 

 red have scarcely any eflTect. 



When an amoeba comes in contact with a well- 

 defined area of light composed of rays perpen- 

 dicular to the slide, it usually stops and proceeds 

 in a diilerent direction. 



In a horizontal beam of direct sunlight they 

 orient fairly accurately. Changing the direction 

 of the rays produces a change of intensity on the 

 surface, but this causes no apparent retardation 

 in any pseudopods. Nor does difference in light 



