212 H. P. KJERSCHOW-AGERSBORG. 



A (or VI.) is the median posterior ray (Fig. /), while ray IV. is 

 in the lead. Figs. 4 and 5 show the relation of the madreporite to 

 the physiological anterior end in young specimens of Pycnopodia; 

 the apical ray, e.g., ray IV., is uppermost on the page (Fig. 4). 

 In Fig. 5, A represents the oral view. Ritter and Crocker ac- 

 cepted as anterior end that pole of the star which corresponds to 

 the larval lobe organ (Fig. 6, Lo) , but if the physiological anterior 

 end in Pycno podia corresponds to the posterior end of the common 

 starfish, then the larval lobe organ has nothing to do with it, at 

 least not in P\cnopodia. It is, of course, an open question whether 

 the anterior rays (II., III., IV., V., I., Fig. 3) correspond to the 

 posterior rays of the same numbers in Ritter and Crocker's sketch 

 (Fig. 2). If they do not, then the physiological anterior end in 

 the adult Pycnopodia has become established independently of the 

 factors as noted above. .But this may not be the case. Of course, 



JL 



FIG. 9. Diagram to show the morphological groundplan of the common 

 starfish. Ill, anterior end; an, anus; mdp, madreporite; o, morphological 

 center; 1-5, interradii ; I-V, radii. (From Delage and Herouard.) 



the common starfish may indeed move with any of its rays in the 

 lead (Jennings, '07, p. 155) ; and "do the same thing, under the 

 same conditions, in a number of different ways, and never do the 

 same thing twice in exactly the same way" (Coe, ('12)). The 

 anterior ray of these species of starfish (Astcrias forrcri, A. for- 



