188 CARNEGIE INSTITUTION OF WASHINGTON. 



The Tortugas surpasses all other marine stations in the purity of 

 its ocean water, in the nearness of its coral reefs, and in having in 

 Cassiopea a coelenterate unmatched as an object for experimental 

 studies. Accordingly, the efforts of a group of students at Tortugas 

 have this year been directed toward acquiring a fuller knowledge of the 

 nature of the chemical equilibrium of the CO2 of sea-water and of the 

 effects of this agent upon growth, regeneration, and the rate of nerve 

 conduction in Cassiopea. 



Dr. Shiro Tashiro devised a method which demonstrates that 

 although sea- water is normally alkaline, yet it contains a substance, 

 probably free CO2, which dissolves calcium carbonate. In confirmation 

 of this Mayer showed, as a result of placing shells in sea-water for one 

 year, that calcium carbonate is dissolved at a slow rate by sea-water 

 which, during the process of solution, remains alkaline. The rate of this 

 solution is, however, so slow that it would require at least 1,000,000 

 years to dissolve off a thickness of 6 feet of calcium carbonate, and 

 as most lagoons are about 20 fathoms deep and are geologically of 

 recent formation, they can not have been dissolved out by sea-water 

 as such. 



A weak concentration of the H ion of free CO2 is a powerful stim- 

 ulant augmenting the rate of nerve conduction in Cassiopea, whereas 

 in higher concentrations, the hydrogen ion becomes a depressant. 

 Thus, if sea-water be shghtly diluted with distilled water which con- 

 tains carbon dioxide, it acts as a stimulant which augments the rate 

 of nerve conduction above the normal, despite the reduction in con- 

 centration of sodium, calcium, and potassium. It is thus essential that 

 the distilled water should contain no greater concentration of free CO2 

 than does the sea- water which it is used to dilute. 



Bearing these facts in mind, Professor Goldfarb repeated his experi- 

 ments upon the relative rate of regeneration in Cassiopea in normal and 

 in diluted sea-water, making use of distilled water in which the free 

 CO2 had been reduced by bubbling air through it which had passed 

 through a soda-lime tube, and in which the residual acidity was neu- 

 tralized bj^ sodium hydroxide. 



Professor Goldfarb also studied the efficiency of the sperm of indi- 

 vidual echinoderms in fertilizing the eggs of individual females and 

 found wide ranges in the ratio of fertilized to unfertilized eggs, dependent 

 upon the individuals experimented with. By aging the extruded sex- 

 cells Professor Goldfarb showed that fresh sperm-cells could fertilize 

 the aged eggs, giving a decreasing number of fertilizations as the eggs 

 became older, the decrease being about the same for all females ; and 

 conversely, a fresh egg could reactivate the aged sperm. The many 

 interesting details of these experiments will be found in his report on 

 pages 202 and 206. 



Dr. Shiro Tashiro showed that in Cassiopea, if the marginal sense- 

 organs be intact, the animal gives out more C02than if they be removed, 



