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Ophiuroid-larvse from many different parts of the world. It occurred to. 

 me that this material might, on a careful comparative study of all the 

 larvse, perhaps give some answer to the question, whether it is, upon the 

 whole, possible to distinguish natural groups in the great variety of forms, 

 or whether there is no system at all. The results of this study has fully 

 borne out the expectations. It was found possible to distinguish several 

 very well characterized groups, and there is good reason to expect that 

 future researches will give no less satisfactory results than those obtained 

 from the study of the Echinoid-larvae. 



Besides the finding of several new, interesting larval types the study 

 of this material led to a most interesting observation. It is well known 

 from the observations of Joh. Muller (V. Abhandl. Taf. VII— VIII) that 

 the metamorphosing larva of Ophiothrix keeps its long posterolateral arms 

 unaltered, the young Ophiurid remaining for some time attached to these 

 arms, which thus serve as a floating apparatus. When ultimately the 

 Ophiurid drops off, these two arms still remain in connection and may 

 continue their pelagic hfe for some time, the vibratile band along the arms 

 remaining quite intact. I have often found such "specimens" in consider- 

 able numbers in the plankton samples (PI. XIX, Fig. 6). The same may 

 occur in other larvse, e. g. Ophiopluteus opulentus (PI. XX, Fig. 3). In this 

 latter case, however, it appears that the "larva" does not perish after a 

 httle while, as it must doubtless happen to the Ophiothrix-"\a.vya'\ In 

 the figure quoted a small swelling is to be noticed in the middle, where 

 the two arms join. In other specimens this swelling is considerably larger 

 and shows an indication of a mouth and a vibratile band and there are 

 small postoral (or anterolateral) rods. This can only mean that a new 

 larval body is about to regenerate from the posterolateral arms, after 

 the young Ophiurid has been developed and dropped off. The fact that 

 the posterolateral arms are perfectly developed proves that we have not 

 simply with an abnormal larva to do; it would be impossible that such 

 abnormal larva with the mouth and intestinal organs imperfectly devel- 

 oped and accordingly unable to feed, could have developed these long 

 arms and their supporting rods perfectly normally. It must then, evidently, 

 be accepted as an established fact that a regeneration of the larval body 

 has taken place here. Whether it would ultimately proceed so far as to 

 result in the formation of a normal new larval body and then a second 

 metamorphosis, must be left an open question; this could probably be 

 ascertained only from a study of hving material. But the fact here 

 estabhshed that a regeneration of the larval body begins after the com- 

 pleted metamorphosis and may be carried quite a long way is of consider- 

 able interest. 



