DEPARTMENT OF MARINE BIOLOGY. 195 



1 meter in depth and another lot on a reef in water 6 meters deep. At the 

 end of a period of one year the measurement of the specimens on these tiles 

 showed that a considerably more rapid growth had been made by the speci- 

 mens in the shallow water than by those at the greater depth. Since, from 

 the nature of their immediate surroundings, it seemed probable that the 

 food-supply of the specimens in deeper water might be less abundant than 

 that of those on the shallower reef, the specimens from both locations were 

 transferred to a reef at a depth of about 4 meters, where the conditions 

 would be practically identical for each of the specimens. As specimens of 

 each species of gorgonian as great in size as any of those on the reefs in 

 deeper water could be found on all the reefs in this last-mentioned depth, 

 it is apparent that the generally larger-sized deep-water gorgonian fauna 

 depends on some factor other than depth alone. The fact that the greatest 

 percentage of large specimens is to be found on the deeper reefs and on the 

 lagoon side rather than on the Gulf side of most of the reefs points to greater 

 protection from wave-action in time of storms as being the most important 

 factor in determining the character of the alcyonarian fauna of any reef. 



Studies on the Physiology of the Nervous System of Cassiopea xamachana, 



by L. R. Gary. 



A. Influence of the Marginal Sense-Organs on Rate of Regeneration. 



The results of my earlier studies^ have shown a marked influence of the 

 sense-organs on the rate of regeneration in Cassiopea xamachana Bigelow, 

 when halves of the same individual disk were used for comparison. In the 

 previous experiments the halves of each disk were insulated by removing 

 two strips of subumbrella ectoderm (which contains the nerves and muscles) 

 from opposite sides of the disk, while the regeneration was measured inward 

 from the periphery of a cavity, where a circular piece of tissue had been 

 removed from the central part of the disk. In all of the experiments carried 

 out this season each disk was cut into halves and the regeneration was 

 measured from the periphery of a cavity left by the removal of a circular 

 piece of tissue 22 mm. in diameter that was cut from a corresponding part 

 of each disk. By this procedure the difficulties in securing accurate measm'e- 

 ments of the regenerating tissues, so frequently met with in my earlier experi- 

 ments, were done away with. 



Two series of experiments were carried out primarily to study the regen- 

 eration. The remaining observations on this question were made upon 

 material used primarily for another problem (section B, below). 



In the first series of experiments 3 sets of 40 disks each were divided into 

 halves and the same operation performed on the halves of each disk. In 

 one set all of the sense-organs were removed for both half-disks and a circuit 

 wave of contraction maintained in a labyrinth of subumbrella tissue of both 

 half-disks. In another set all sense-organs were removed from both halves 

 and both of them allowed to remain inactive. In the third set a small piece 

 of tissue was removed from between the sense-organs of each half-disk which 

 retained its full quota of sense-organs. This extensive "control" series 

 was undertaken to ascertain the limits of variation in the rates of regenera- 

 tion shown by the two halves of the same disk under the conditions existing 

 during the course of the regular experiments. The results from these experi- 

 ments showed that, under either of the three operations mentioned, the 



^Cary, L. R., Year Book Carnegie Institution of Washington, Nos. 13 and 14; Proc. Nat. 

 Acad. Sci., vol. 1, No. 12; Jour. Exp. Zool., vol. 21, No. 1. 



