vm EGHINODERMATA — REGENERATION, ETC. 505 



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

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

 wall. 



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

 solves into slime. A Stichopus 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, Ophidiaster diplax. A specimen witli the arms (3, 4, S) in tlie <aet of being re- 

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

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

 (after Haeokel). C, Tlie case given in the text of a specimen of Linckia multifora (after P. and F. 

 Sarasin). 



enclosing the viscera remained. That regeneration follows such a phenomenon has 

 not yet been established by observation. 



The Synaptidce react on stimuli (often i^uite 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 be 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 lias had as a consequence ase.xual reproduction. 

 It is, indeed, not certain that, in the cases to be quoted below, the division into 



