DEPARTMENT OF MARINE BIOLOGY. 199 



Key was noted where there were 75.7 dead gorgonians to the square yard 

 over a considerable area. On the basis of the analyses recorded above, this 

 would mean the deposition of at least 25 pounds of spicules per square yard 

 and probably a considerably larger amount, as all of the dead specimens were 

 of large size. Under normal conditions a considerable number of the axial 

 skeletons of dead colonies are present on the reefs, but the rate of disintegra- 

 tion of this portion of the colony is not sufficiently well known to the wiiter 

 to afford the means of ascertaining how long such a colony has been dead, 

 which would make possible an estimate of the amount of material actually 

 added to the reefs by the gorgonians. 



Studies on Regeneration: The Influence of the Sense-Organs on the 

 Rate of Regeneration in Cassiopea xamachana. 



A series of experiments carried out at the Tortugas Laboratory during 

 September 1913 showed that when the sense-organs were removed from one 

 half of a Cassiopea disk, an equal amount of tissue from between the sense- 

 organs on the opposite side, and the two halves insulated by the removal of 

 two narrow strips of subumbrella ectoderm from between them, regeneration 

 took place more rapidly from the half that bore the sense-organs. The rate 

 of regeneration was measured inward from the periphery of a circle where the 

 tissue had been removed from the center of the disk. 



These experiments showed further that if only a single sense-organ was left 

 on one half of a medusa disk the regeneration was faster from that side and 

 was, indeed, as rapid as though the 8 sense-organs normally present had been 

 left intact. 



No time was then available to carry on further experiments and the data 

 at hand seemed to me to indicate that the muscular activity and consequently 

 higher rate of metabolism of the half disk bearing sense-organs was directly 

 responsible for the higher rate of regeneration. 



During the summer of 1914 experiments involving some 500 medusa disks, 

 prepared so that one half was active, the other inactive, have confirmed the 

 previous results. 



Disks prepared in the manner mentioned above were allowed to regenerate 

 in sea-water to which had been added 15 parts of O.Qm. MgS04. In this 

 medium the disks continue to live and regenerate, but are unable to pulsate. 

 Under these conditions the rate of regeneration was equal from both halves 

 of the disk, although slower than in normal sea-water. Other individuals were 

 treated with varying concentrations of oxalic acid which will destroy the sense- 

 organs. In practically all instances, however, when either the concentration 

 of the acid was high enough or the time of exposure to lower concentrations 

 long enough to destroy the sense-organs, the other tissues of the medusa v/ere 

 irreparably injured, so that these experiments were of no value. 



In order to eliminate the sense-organs and still retain muscular activity in 

 one half of the disk, all sense-organs were removed, the halves insulated by 

 removal of a strip of subumbrella ectoderm, and a trapped wave of contraction 

 maintained in one half of the disk. This was accomplished in the manner 

 previously described by Mayer, by so cutting the subumbrella tissue that when 

 the contraction wave is started by induction shocks it is transmitted through 

 an endless labj^rinth of muscle tissue. After a short time the contraction 

 wave assumed about the normal rate of pulsation of the uninjured medusa. 

 By going over the specimens daily and cutting again wherever the wound had 

 healed over, the stimulated half could be kept active for several days until 

 the regeneration of the central cavity Avas completed. In all the specimens 



