Il8 H. H. NEWMAN. 



structures that subsequently regress and give place to left-hand 

 hydropores, as Gemmill claims to be the case for Asterias rubens, 

 but are permanent asymmetrical structures that remain up to the 

 point of metamorphosis. In every culture observed the right- 

 handed individuals maintained their reversed asymmetry and 

 developed on the average as normally as did the more typical 

 left-handed larvae; in fact one gets the impression that in some 

 cases at least, the reversed larvse are a little larger and more active 

 than the typical ones belonging to the same lot. 



This is, I believe, the first time that large numbers of indi- 

 viduals with right-handed (reversed) asymmetry have been de- 

 scribed for echinoderms. Only very rare and sporadic instances 

 of reversal of asymmetry have been reported. In Poramis, a 

 species of starfish studied intensively by Gemmill, double hydro- 

 pores occurred in about 50 per cent, of the larvse, but he specific- 

 ally states that but "a single instance was observed in which the 

 hydropore occurred on the right side alone." It may be perti- 

 nent, however, to recall that Oshima found both in control 

 laboratory cultures and in experimental cultures of Echinus 

 miliaris about 10 per cent, of specimens with right-hand asym- 

 metry. In these experiments, however, it must not be forgotten 

 that both controls and experiments were conducted under dis- 

 tinctly abnormal conditions, since artificial sea-water was used 

 and the food was unsatisfactory. The possibility is not to be 

 denied, however, that this species of echinoid may exhibit 

 normally a fairly high degree of reversed asymmetry. 



From what has been said, it may be inferred that Patiria 

 miniata is in a somewhat delicate state of organic equilibrium 

 with regard to its asymmetry, and should, therefore, furnish ideal 

 material for an experimental analysis of the nature of this 

 asymmetry. 



The Development of the Hydroccele and its Rays. Although one 

 may observe by the end of the first week or ten days a posterior 

 prolongation of the left (in reversed larvae, the right) anterior 

 coelom, this structure does not thicken up and become obviously 

 a hydroccele until about the end of the third week. In fact, a 

 hydrocoele never develops unless the larvae are well fed and 

 otherwise well cared for. The hydroccele appears at the same 



