DEIPARTMENT OF MARINE BIOLOGY. I29 



hard to explain, unless it be assumed that the oral surface is much more 

 sensitive to bright light than the aboral surface. 



(6) The above explanation receives support from a series of experiments 

 showing that when the intensity of the light is reduced — i. e., much less than 

 ordinary diffuse daylight (about 10 candlepower) — the tendency to right 

 away from the source of light is not nearly so strong. 



(7) BcJiinastcr tends to right itself away from the light even though in so 

 doing it has to turn up a slightly inclined plane (4° 30'). 



(8) While all my experiments lead to the belief that the direction of loco- 

 motion of Bchinaster is determined by the relative intensity of the light rather 

 than the direction of the rays, yet a series of experiments were undertaken 

 using a special apparatus into which was admitted light of a graded intensity. 

 Many trials with this apparatus showed conclusively that Bchinaster moves 

 from place to place guided by the relative intensity of the light striking the 

 different parts of the body and not by the direction of the light rays. 



(9) A change of temperature does not change the sign of the reaction to a 

 source of light. Bchinaster moves toward the source of light when the tem- 

 perature is kept anywhere between 64° and 94° F. At the two extremes, 

 however, the response is very weak. 



(10) Experiments made with various color-screens indicate that no one 

 kind of ray is necessary to stimulate Bchinaster. The following five screens 

 used cut out: (a) ultra violet; (&) ultra violet and violet; (c) violet and 

 blue; {d) green, yellow, orange, and red; {e) ultra red. 



(11) When the tip of each ray is amputated, this starfish still rights itself 

 away from the source and then moves toward the source of light, just as in 

 normal individuals. This shows that the eye-spots are not necessary in the 

 reactions of Bchinaster to light. 



A detailed account of the experiments upon which the above conclusions 

 are based, together with an account of experiments using the starfish Astro- 

 pecten duplicatus and the ophiuroid Ophiocoma riisei, will soon be published 

 by the Carnegie Institution of Washington. 



Preliminary Report of Researches at Tortugas, June and July, 1909, by 

 B. Newton Harvey, University of Pennsylvania. 



(l) The Temperature Coefficients of Some Life Processes, and the Effect of Electro- 

 lyte Solutions on the Medusa Cassiopea at Different Temperatures. 



A Study was made of the pulsation-rate and the rate of nerve-conduction 

 in Cassiopea xamachana at different temperatures. Before beginning this 

 work, the upper and lower temperature-limits of muscle-contraction, nerve- 

 conduction, and the origination of pulsation in the sense-organs were deter- 

 mined. All of these can be very readily separated in this animal. It was 

 found that contraction stops at 10.6°, conduction at 9.5°, and pulsation at 

 14° to 15°. This stoppage is reversible to about 7° to 8°, when the tissues 

 do not recover, but disintegrate on warming. This adds another example to 

 the list of irreversible changes occurring in tissues at low temperatures but 

 above the freezing-point. The upper temperature limits are 39.5° for 

 muscles, 44° for nerves, and 42.6° for sense-organs. At 44.5° recovery of 

 conduction does not occur on cooling. There is evidence that all the above 

 temperatures are a function of time and the condition of the medusa, so they 

 can only be approximate. The temperature of the water in which Cassiopea 

 lives varies not more than 3° either side of 30° C. in summer. 



