COMPSOMETRA SERUATA. 23 



As seen in text-figure 3, the oralia are still fairly large and of a very peculiar 

 shape, with a prominent point, bent towards the mouth. 

 The skin of the oral disk otherwise contains numerous 

 fenestrated plates, among which is a large anal plate 

 (not in the figure). The primary hydropore is seen 

 in the anal interradius; each of the other interradii 

 has some 5 to 10 hydropores (situated outside the 

 part figured), while in the anal interradius there is still 

 only the primary pore. A larger plate is found in the 

 lower part of each interradius, in the corner between 

 the costals. The basalia have already completely 

 disappeared from the outside of the calyx and formed Fig 4.-SpicuieB from the 



*^^ . . , rr, r. , oral disk of a grown Iropio- 



the rosette, as may be seen from the mside. ihetrst ,„etra. x20o. 

 cirri are seen to be radial in position. 



In the grown specimens the oral plates as well as all the other fenestrated 

 plates have disappeared, and instead the skin has been studded with small, 

 more or less bone-shaped spicules (text-figure 4), inextricably entangled. 



II. COMPSOMETRA SERRATA (A. H. Clark).'^ 



(Plates XI to XIII.) 



This species was found to be fairly common on the rocky shores near the 

 biological station at Misaki, from about low-tide mark to somewhat deeper 

 water. It was often found on the under side of rocks which one could turn 

 over, and also among the roots of Laminarians and other algae. Although I 

 examined many specimens very carefully and kept them in jars for some time, 

 I did not succeed in finding any with eggs or embryos on the pinnule. Then, 

 to my great surprise, I found, on my return, on examining the preserved 

 specimens, a few with a good number of embryos on the pinnules. They 

 proved to be of only two difTerent stages, no intermediate stages being repre- 

 sented. This proves that in this species, as in Antedon, the eggs are laid 

 contemporaneously by different individuals, apparently on account of the 

 stimulating effect of the sperm emptied by some male specimen. I had 

 at that time never studied the embryology of any Crinoid, otherwise I 

 would probably have succeeded in getting specimens to discharge their eggs, 

 so that the complete developmental history would have been obtained. 

 However, the two stages obtained give such valuable information of the 

 embryology of this species that a description seems worth while, the more 

 so as I secured good material for the study of the postembryonal development 

 of the species. With the exception of the very youngest stages of the embry- 

 ological development, I can thus give the developmental history of this species 

 almost completely. ^ 



" I am indebted to Dr. A. H. Clark for the identification of this Bpecies. 



