121 



Ophinioid-larv.T Irom iiiaiiy difTeiciit parts of the world. II occurred to 

 iiic llial I his material iiii^hl, on a carelul coin|)arative sluily ol all the 

 larvee, perhaps j^ive some answer to the question, whether it is, upon the 

 whole, possible lo 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-larvse. 



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 .Job. Miiller (V. Abhandl. Taf. VII— VIII) that 

 the metamorphosing larva of Ophiolhrix 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 ofT, these two arms still remain in connection and may 

 continue their pelagic life 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 larva;, e. g. Ophioplutciis opuknlus (Fl. XX, Fig. .'3). In this 

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

 little while, as it must doubtless happen to the Ophiolhrix- '\aiwa\ 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 ofT. 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 

 inetam()r|)ii()sis, must be left an oj)en ([uestion: this could ])robably be 

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

 established 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. 



