THE TWENTY-RAYED STARFISH. 



211 



which bears the anus. Ray IV. records 107 trials, ray III. 137, 

 and ray II. 103 trials out of the total of 499; while rays V. and I. 

 have only 74^/2 and 77j/2, respectively. This is, indeed, a very 

 striking contrast to Ludwig's so-called " vorderer Interradius," 

 e.g., interradius I. -I I., the ipso facto posterior end. If the physi- 

 ological anterior rays of Pycnopodia arc in fact the morphological 

 anterior rays, as represented by Ritter and Crocker (although 

 theirs must be inverted), then all facts agree. (Compare Figs. 2, 

 3, and 7.) In Pycnopodia the line of bilateral symmetry lies along 



B 



FIG. S. Diagram to show the physiological anterior end of Asterias 

 forbefi, and its relation to the madreporite. Line AA I plane of bilateral sym- 

 metry ; BB, dissects the star into an anterior and posterior pole according to 

 direction of locomotion. The number at the end of each ray indicates the 

 exact number of attempts the star used that ray as " anterior " ray in locomo- 

 tion ; ray e, is seen to have the largest number in its favor. (Ray 2 = III, 

 Cuenot.) The sum of the trials indicates a " right " and " left " which cor- 

 respond very well to a plan of bilateral symmetry. (From Cole.) 



the rays IV A (ray A = VI.) ; this is explainable by the fact that 

 five of the six primary rays become the anterior rays, with ray IV. 

 in the lead, and rays III., II. on the left, and V., I. on the right 

 (Fig. 7). The relation of the madreporite and of the anus to the 

 clorso-radial muscles is then demonstrated (Figs. 2 and 3). Ray 



