292 W- J- Crozier, 



the earthworm, and support the view that the physiology of ,.taste"^ 

 in vertebrates is different in essential particulars from that in in- 

 vertebrates. 



11. 



The present paper has been devoted to the description and 

 interpretation of a series of individual reactions. It must be em- 

 phasized, however, that both in the laboratory and under the natural 

 conditions of life these separate reactions of Holothitria are welded 

 into an harmonious behavior, which is closely correlated with the 

 animal's passively defensive mode of existence. Morphologically the 

 holothurians are set apart from other echinoderms by the immense 

 development of their muscle equipment and the concomitant re- 

 duction of the calcareous exoskeleton. It is this prominence of the 

 muscular system which gives to the behavior of Holothuria a kind 

 of unity not seen, so conspicuously at least, in other echinoderms. 

 As far as its behavior is concerned Holothuria surinamensis is a 

 bilateral anim.al; the restriction of pedicels to its functionally ventral 

 surface helps to accentuate this. Its direction of progression is 

 definitely fixed; it always moves with the anterior end in advance. 

 The tentacles, pedicels and papillae are, to a certain extent, in- 

 dependently controlled; but as a whole the flexibility of the animal 

 and the possibility of coordination, even in the absence of the nerve 

 ring, makes Holothuria much less a "republic of reflexes" (v. Uexküll) 

 than is the case with the sea-urchin or starfish. 



