82 Papers from the Marine Biological Laboratory at Tortugas. 



direct influence over the regeneration rate through its control of the ani- 

 mal's movements. The experiments recorded above, however, seem to 

 contrast (in a manner only possible on some such unique form) the effects 



Fig. 28.' — Ring from which disk center has been cut away. .1 : so, sense-organs cut away 

 from upper half; from lower half equal-sized pieces have been removed. X, insula- 

 tion between halves. B: Stippled area shows rate of regeneration to be equal from 

 the two. 



of activity and rest, and the results show in a decided way the negative 

 influence of the two conditions. If such facts apply to the animal kingdom 

 generally, then Child's idea that the regulation of growth is controlled by 

 these factors is insufficient to account for the observed phenomena. 



THE RELATIONSHIP BETWEEN THE NUMBER OF REMOVED MOUTH- 

 ARMS AND THEIR RATES OF REGENERATION. — DOES THE REGEN- 

 ERATION RATE OF AN APPENDAGE VARY DIRECTLY V^ITH THE 

 EXTENT OF INJURY? 



The conclusion that the animal with the greater number of removed 

 parts regenerates each part more rapidly than does the one with the lesser 

 number of removed parts was suggested by Zeleny (1903, 1905) and sup- 

 ported by his studies on several forms. He (1903) found in Ophioglypha, 

 the brittle-star, that when three or four of the arms were removed from 

 an individual each arm would regenerate faster than would the arms of an 

 individual with a smaller number removed. The difference in rate was 

 sufficient to be shown in his text-figures (1905, fig. 4). The arms of this 

 star-fish are all similar in size and form, and thus the regenerating bud 

 from the base of any one may be compared with that from the base of any 

 other. Such an animal also regenerates the arm-buds by a process of 

 continuous growth. No criticism that I know of can be cited against these 

 observations on Ophioglypha nor against Zeleny's conclusion that in this 

 species at least the rate of regeneration is fastest in the series which has 

 undergone the greatest injury, except possibly the objection that the series 

 consisted of too few individuals. It may be that while in one group of 

 animals results similar to Zeleny's would obtain, in another different results 

 might follow. This can only be ascertained by further observations. 



It will be shown below, from a study of several series of Cassiopea, 



