204 



H. P. KJERSCHOW-AGERSBORG. 



qui depends de 1'anus est alteree par le madreporite. 



" Quand on regarde 1'animal par la face dorsale, 1'interradius 

 madreporique vient apres 1'interradius anal, separe de lui, d'un 

 cote, dans le sens indirect (inverse de celui de la succession des 

 heures sur un cadran), par un seul interradius, de 1'autre par deux 

 interradius," p. 2. 



"... quand on regarde 1'animal par le pole apical, 1'anus est en 

 arriere, le madreporite en avant et a droit," p. 3. 



IX A ** 



FIG. 2. Ritter's and Crocker's figure of the dorsal radial muscles of Pycno- 

 fodia lielianthoides, showing the relation of the radial muscles to the asteroid 

 groundplan. as represented in Fig. i. A, the "anterior" ray; I-V, the "pos- 

 terior " rays ; r.r-r.r-,. rays added, on the right side, to the original six rays 

 after metamorphosis; /.r /.r 7 , rays added to the left side; a, anus; Mp, mad- 

 reporite. 



Shipley ('93), MacBride ('96), and Lankester Coo) do not 

 commit themselves in regard to the position of the madreporite, 

 i.e., as far as the starfish is concerned. 



Ritter and Crocker ('oo) in their work on Pycno podia adopted 

 Ludwig's and Agassiz's plan of numbering the radii of the typical 

 five-rayed echinoderm. According to this, when the apical side is 

 uppermost, counting from the madreporite clockwise, the rays are 

 numbered from I.-V. These authors go on by saying: "From a 

 study of the metamorphosis, Ludwig, '82, considers that the star 

 should be oriented by a line running interradially between I. and 

 II. and radially along IV., thus bringing the madreporite in the 

 left anterior interradius" (Fig. i). 



