126 REPORTS ON INVIvSTlGATlONS AND PROJECTS. 



these reaction-changes can be brought about in one and the same individual, 

 or whether generations must elapse before acclimatization is accomplished. 



In another research the Director studied the starvation of Cassiopea xama- 

 chana. In general, the loss of weight during the day is proportional to the 

 initial weight at the beginning of the day. Hence the weight of the starving 

 medusa is represented by the formula y=lV{i-a)'', where y is the weight 

 upon any given day, W the weight of the medusa when starving began, 

 W{i-a) the weight at the end of the first day of starving, a being a constant 

 and X the number of days starving has continued. The medusae, if starved 

 in diffuse daylight, can survive 41 days and be reduced to 1/142 their origi- 

 nal weight. They lose weight more rapidly, and do not survive as long in 

 the dark as in light, and in the dark their parasitic algal cells become greatly 

 reduced in number, although not entirely killed. Also, in the dark the me- 

 dusa gives out much more COo than in the light, and it is evident that the 

 oxygen set free by the algal cells in daylight serves to sustain the medusa, 

 while the CO2 serves to maintain the plant cells. 



Medusae starved in the dark decline in weight in fair accord with the 

 formula y^=W {\-a)'^ ; but if starved in dififuse daylight their loss of weight 

 for the first 20 days is slower, and the medusae remain heavier than should 

 be expected according to the above-mentioned formula. Thus it appears that 

 the medusa effectually feeds upon its algal cells, which multiply and main- 

 tain an internal source of food for their host. In the dark, however, these 

 algal cells do not reproduce, and are soon reduced to a practical zero, thus 

 failing to sustain the medusa. This probably applies also to the stony corals 

 and actinians as well as to rhizostomous Scyphomedusse. 



In another research the Director investigated the interactions between the 

 cations sodium, magnesium, calcium, and potassium in producing movements 

 in marine invertebrates. Calcium can not produce tetanus in the absence of 

 sodium ; hence the so-called "calcium tetanus" is probably produced by the 

 chemical combination of calcium and sodium with a proteid. The stupefying 

 effect of magnesium is cumulative, increasing with the increase of concen- 

 tration of the magnesium ion ; but this does not apply to calcium, for this 

 produces almost its normal effect very suddenly upon attaining a certain con- 

 centration, and increasing the pressure of the Ca ion beyond this has rela- 

 tively little eft'ect. 



Mechanical pressure upon the subumbrella of Cassiopea reduces its sensi- 

 tiveness to stimuli ; hence a contraction-wave produced by a stimulus travels 

 from an unpressed, or recently pressed, to a pressed or long pressed place, 

 whether this be from cathode to anode or from anode to cathode. 



Medusae which under normal conditions pulsate about 45 times per minute 

 maintain a rate of 129 if made into a circuit-ring, and this ring is capable of 

 responding to 152 induced shocks per minute by 152 pulsations for an indefi- 

 nite time, or 252 shocks for about 2^^ minutes. Thus the nerves are capable 

 of transmitting and the muscles of responding by contraction to more than 



