185 



But on a less careful preservation the result will mostly be very poor; 

 which accounts for the fact that Asteroid larvae from plankton samples 

 are generally of little use, being often unidentifiable, in contradistinction 

 to the Echinoid- and especially the Ophiurid-larvse, where the skeleton 

 affords sufficient characters for identification, so that such larvae may be 

 very well utilized, even if the soft parts of their bodies are in a poor state of 

 preservation. — In the present work I have made little use of such material 

 of Asteroid larvae from plankton samples, although 1 have quite a good 

 deal of them, some of them representing types of Bipinnarise hitherto un- 

 known. They are, however, not of so considerable importance that I deem 

 it desirable to publish descriptions of them, which cannot be in any way 

 satisfactory. 



Astropecten scoparius MuUer & Troschel. 



PI. XXXIII, Figs. 3—5. 



This species, which occurs abundantly in shallow water near the Bio- 

 logical Station at Misaki, was found to have ripe sexual products in June; 

 fertilization was undertaken on June 21st 1914, the sperma being treated 

 with NaOH. The embryo is in the blastula-stage very much folded, look- 

 ing almost like a walnut, the folds disappearing when the embryo leaves 

 the egg-membrane. I have no notices on the progressive development of 

 the embryos, so that the details of the transformation of the embryo into 

 the Bipinnaria-larva cannot be given. At the age af 7 days they had devel- 

 oped into beautiful Bipinnariae, the enterocoel pouches having, however, 

 not yet united in the anterior end of the larval body. At the age af 19 — 21 

 days the larvae were in beginning metamorphosis. Beyond this stage it 

 was not possible to rear them, my stay at Misaki ending by that time. 



The larva (PI. XXX I II, Figs. 3 — 5) is of a very typical Bipinnaria-shape, 

 with short, rounded processes. The preoral band forms a high arch, while 

 the postoral band curves only slightly downwards in the middle. The 

 postoral processes are very distinct, as are also the posterolateral, postero- 

 dorsal and anterodorsal processes. The median processes are of about equal 

 size, short, rounded, the ventral one being somewhat ventrally directed 

 (this accounts for its apparently being much shorter than the dorsal pro- 

 cess in Fig. 5). Preoral processes are not distinct, the frontal area only 

 being narrowed at the base of the median process, especially so in the 

 metamorphosis stage; also at the base of the dorsal median process there 

 is a distinct narrowing, the vibratile band from the two sides sometimes 

 nearly joining in the midline. The frontal area is distinctly convex, the 

 sides lying much deeper than the middle part, as is especially distinct in 

 the metamorphosis stage. — There is a distinct suboral cavity, narrow 



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