DEPARTMENT OF MARINE BIOLOGY. 



197 



In my experiments the two halves of a series of disks were compared 

 upon which there had been performed one of the three types of operations 

 regularly used in the previous regeneration experiments. By means of these 

 operations a comparison was made between the halves of a given disk, one 

 of which retained its sense-organs, while these were removed from the other 

 half (active and inactive series). In a second operation the rhopalia were 

 removed from both half-disks, while one of them was activated by means 

 of a circuit wave of contraction maintained in an endless labyrinth of sub- 

 umbrella ectoderm (activated and inactive series). The third set consisted 

 of disks one half of each with its sense-organs to control contraction, while 

 the other half was activated by a circuit wave of contractions in its subum- 

 brella muscles. 



In the first type of experiment the loss was always greater for the half 

 with its sense-organs than for the inactive half, as shown in table 3. 



Table 3. — Differences in loss of weight in active and inactive half-disks. 



The weights given in tables 3, 4, and 5 are reduced to terms of 100 grams 

 at the beginning of the experiments. 



As will be noted, for each set of half -disks the loss is greatest for the first 

 day and becomes progressively less throughout the experiment. The actual 

 difference in the amount of the loss becomes very much less as the experi- 

 ment is prolonged until at the fourth day after the operation both halves 

 have lost approximately 55 per cent. Both of these features of the results 

 resemble very closely those obtained in regeneration experiments. Thus 

 the sense-organs appear to affect the loss of weight in much the sarne manner 

 that they do the rate of regeneration, at least a graphic expression of the 

 results obtained by the two methods are closely similar to one another. 

 These results support my previously expressed views that the rate of regen- 

 eration is one expression of the general metaboHsm of the medusa, and as 

 such is under the influence of the nerve-centers. 



When a comparison is made between the rates of loss of half-disks with 

 sense-organs and those activated by a circuit wave of contraction, as shown 

 in table 3, it is seen that the activated half-disk loses weight to a considerably 

 less extent than does the half with sense-organs. 



On the other hand, the muscular activity of the activated half-disk was 

 never less than three times that of the half with sense-organs. As the experi- 

 ments progressed, the difference in the rate of pulsation constantly became 

 greater. The rate of the half-disks with sense-organs usually fell, ^yithin 

 24 hours from the time of operation, to less than half the rate immediately 

 after the operation; on the contrary, there was commonly an increase in the 

 rate of pulsation of the activated half within the first 24 hours, after which 

 it remained practically constant. In the third, fourth, and fifth days of 

 any experiment the pulsation-rate of the activated half of any pair of half- 

 disks was frequently more than ten times the rate of the other half of the 

 same disk upon which the sense-organs remained. 



