Ko. 038] SHORTER ARTICLES AND DISCUSSION 



279 



the degree of intactiveness of the photoreceptive apparatus, and 

 its importance in the present connection is due to the fact thai 

 the chitons of intermediate age, eroded to a moderate degree, 

 and less photonegative^^ tlian the smaller ones, come to occur in 

 places where moderate illumination prevails. Moreover, they 

 move about much more freely than the younger individuals, thus 

 often getting some distance away from loose rocks, not plentiful 

 along many stretches of shore line. Crevices of one sort or 

 another, or shaded depressions, are therefore the one type of 

 refuge open to them. 



;j. It was found, by observing a group of marked chitons each 

 day for a month, that the older ones and those of the "inter- 

 mediate"' group do not wander readily from place to place 

 (Arcy and Crozier, 191!)). Another group containing 14 chitons 

 of the "intermediate" class as above defiiunl was under daily 

 oliservation fur three months, and the behavior of this group 

 stror.uly suouvsTe.l a feehle kind of " " h.-min- ' ' phenomenon. The 

 animals eniu-eniea .pmi ino>t of ihe .lay under a boulder at 



than a meter, feeding on !■ nfn-umorpha and other alga>. With tlie 

 risin- s„„. tih'v ivtreatrd m ;he roek-shelter. If the tide wore 

 out al Minrise. they renniined more or le.^s fixed until again cov- 



This" sort of behavior, regularly and constantly exhibited, 

 seemed to represent perhaps the incipient stages of a kind of 



