208 



H. P. KJERSCHOW-AGERSBORG. 



madreporite is still in the interraditis V.-I. of Ludwig. The posi- 

 tion of the anus, in fact, corresponds, now, with Delage and 

 Herouard's asteroid plan. Figure 2 is copied from Ritter and 

 Crocker ('oo) and represents a diagram of the muscles of the 

 aboral disk, seen from the inside, and as though looked down upon, 

 showing the apical radial muscle bands, the madreporite, and the 

 position of the anus close to the origin of the muscle of ray A 

 (VI.). If ray A were the anterior end, then the anus would be 

 anterior to the center of the dorsal side; but since ray A is, in fact, 



A JF 1L B 



FIG. 5. Young individuals in the i2-rayed stage to show the interpolation 

 zones : r.r2-/. r i. These figures are as per the original and show the reverse 

 condition as in Fig. 4, which has been inverted to show the right relation of 

 the madreporite to the true anterior end. A, oral view ; B, aboral view. 

 (From Ritter and Crocker.) 



the posterior ray, the anus becomes placed posterior to the mid- 

 dorsal point. Delage and Herouard ('03) adopt Cuenot's plan 

 ('91), with the madreporite in the interradius III.-IL ; the anus in 

 interradius II.-L, a little posterior of the mid-dorsal, but also a 

 little to the right of the median line (Fig. 9). This seems to be 

 an arbitrary matter of orienting the star. If the interradius I. -II. 

 of Cuenot is placed as anterior end, the anus comes in the similar 

 position as in Ludwig's plan : the madreporite is in interradius II.- 

 III.; the anterior end is ray III. (Fig. 9). My drawing of the 

 radial aboral muscles does not correspond at all with Ritter and 

 Crocker's, in the point of orientation, and, in fact, also in the points 

 relative to the general radiation of these muscles. I have com- 

 pared the arrangement of the apical radial muscles in both large 

 and small individuals having the same relative number of rays and 



