VIII 



EOEINODERMA TA—REGENERA TION, ETG. 



505 



so violently that the intestine is torn out (usnally behind the calcareous ring), and 

 together with the right respiratory tree is ejected through a rent in the cloacal 

 wall. 



In certain Holothurioiclea, the integument, when strongly irritated, easily dis- 

 solves into slime. A Stichopiis was observed to come entirely out of its skin, i.e. 

 the whole integument dissolved into slime, so that only the dermomuscular tube 



Fig. 397.— a, OpUdiaster dlplax. A specimen with tlie arms (8, 4, 6) in the act of being re- 

 generated ; and two (1 and 2) being constricted off (after Haeckel). B, Linckia (Ophidiaster) multi- 

 fora, a "comet" fonn. One arm is in the act of regenerating the disc and the other four arms 

 (after Haeckel). C, The case given in the text of a specimen of Lincl^ia multifora (after P. and F. 

 Sarasin). 



enclosing the viscei'a remained. That regeneration follows such a phenomenon has 

 not yet been established by observation. 



The Synaptidce react on stimuli (ofteu quite slight) by falling to pieces, the 

 circular musculature being at certain points so strongly contracted that the parts 

 thus constricted break off. 



It will no doubt he proved in time that all these manifestations of increased 

 irritability which coincide with increased capacity for regeneration are of use to the 

 animal. 



Asexual reproduction (schizogony). In certain Echinoderms, the strongly 

 developed capacity for regeneration has had as a consequence asexual reproduction. 



