DEPARTMEXT OF MARINE BIOLOGY. 1 25 



Light and the ^^larquesas. His studies of coral reefs and of the life history 

 and struggle for existence among corals is the most intensive and most 

 carefully controlled yet undertaken, and it will soon become necessar>' for 

 him to extend his field of observation to include the Great Barrier Reef re- 

 gion of Australia in order that his results may become of world-wide signifi- 

 cance. In April and ^lay 1912 we expect that he may visit the Barrier Reef 

 of Andros Island, Bahamas, the greatest coral reef of the Atlantic. The 

 Anton Dohrn, supplem.ented by the Sea Horse and a launch, will constitute 

 a suitable fleet for such an expedition. 



Prof. W. L. Tower's experiments were terminated by the hurricane of 

 October 1910, but with characteristic pertinacity he expects to replant his 

 Solanum and begin anew. It is a rare privilege to the laboratory to lend its 

 aid to him in this difficult investigation. Indeed, it may be said that the 

 course of a worthy research "never ran smooth." yet it is through just such 

 studies that discoveries are made. 



A. G. Mayer conducted several researches — one upon the reactions to 

 temperature of animals which extend from arctic or temperate regions to 

 the tropics. He concludes that in order to sur^-ive in the shallow or surface 

 waters of the tropics an animal must be able to withstand a temperature of 

 at least 29° C, whereas to live in the arctic regions a marine animal must 

 tolerate being frozen into the ice; thus the common Scyphomedusa Aurelli.i 

 aurita ranges from pole to pole, and is found in all oceans, being especially 

 abundant in cold seas. At Halifax, Xova Scotia, it pulsates between —1.4° 

 and 29.7° C, being most active at about 20°, and it survives being frozen 

 solidly into the ice. The same species of Aiirellia at Tortugas, however, is 

 active between '.7^° and 38.4° C, being most active at 28°, and being killed 

 if frozen. Evidently the constitution of the medusa has changed greatly 

 upon its becoming acclimated to the tropics. Similarly, Pennaria at Woods 

 Hole, ^Massachusetts, sur\-ives freezing, whereas at Tortugas it is killed. 

 The rule appears to be that when a cold-water species becomes acclimated 

 to a tropical sea its optimum temperature, death temperature, and tempera- 

 ture of maximum activity are raised, while at the same time it loses the 

 power to withstand cold. Thus apparently some change comes over the 

 colloids which causes them to congeal at a higher temperature in the tropics. 



A typical arctic genus of Scyphomedusae is Cyanea, and C. arctica remains 

 active until frozen into the ice, and is apparently uninjured by this treatment, 

 for it recovers as soon as the ice melts sufficiently to permit it to pulsate. 

 On the other hand, a temperature of 26.5° to 28° is fatal to it, and this 

 accounts for the absence of this genus in tropical seas. 



On the other hand, the rhizostomous medusa Cassiopea frondosa belongs 

 to a strictly tropical genus. It remains active between 12.1° and 40°, and is 

 killed if cooled to 8.3° C. Evidently it could not sur^'ive in temperate seas. 

 The above are only a few of the forms already experimented upon, and the 

 research will be widely extended and the attempt made to determine whether 



