213 



Turning to the Ophiurid-larvae we find mat UTS much less clear than 

 is the case with the Kchinoid-larva 1 . In fact, our previous knowledge would 

 hardly seem to warrant any other conclusion than this, that these larva? 

 form a rather chaotic assemblage; thus e. g. the larva? of forms so closely 

 related as Ophiura af/inis, cilbida and le.rlumta are so difYerenl. that they 

 would rather seem to belong to different families than to closely related 

 species. The present researches, however, tend to prove that matters do 

 not stand quite as badly. 



It may be regarded as an established fact that within the genus Ophin- 

 Ihri.r the larvae are of a very uniform character, so uniform, indeed, that 

 it is in many cases impossible to distinguish the various larval species. 

 Whether this type is peculiar to the whole family of the Ophiothrichida?, 

 and not to the genus Ophiulhri.i- alone, remains to be proved. Hut in any 

 case we have here a distinct larval type common to the very numerous 

 species within this genus, and there is not the slightest reason to believe 

 that the larva? of any of these species should prove to differ markedly from 

 the common type. This is then in perfect accordance with the legitimate 

 claim, that nearly related forms should agree in regard to their larval 

 characters. 



Another conspicuous case is afforded by the Ophiocoma-\arvse. The four 

 (or five) larva? hitherto known are so closely alike that it may be safely 

 stated that there is a distinct larval type of this genus, characterized 

 through the transformation of the central part of the body skeleton into 

 a sort of link, and through the existence of vibralile lobes. Whether this 

 larval type is peculiar also to the family Ophiocomidte remains uncertain. 



The study of the great variety of Ophiuroid larva 1 of unknown origin 

 has disclosed the important fact that also among these larva? several 

 distinctly characterized types may be distinguished, each comprising seve- 

 ral species. After the analogy of the genera Ophiolhri.r and Ophiocoma it 

 may very reasonably be concluded that these types represent various 

 genera, the larva 1 of the different species within these genera being upon 

 the whole closely alike, as should be claimed upon the theory of the classi- 

 ficatory value of the larva 1 . Such larval types are especially Ophioplnleus 

 iinduldliifi, 0. arcifer, (). pnsillus. (). serratus-bimaculatus. 



It is then hardly to be denied that definite proof has been given that, 

 also within the Ophiuroids. the larva 1 of closely related species 

 are in general similar, agreeing in their main characters. The 

 conclusion to be derived from this fact must needs be this that the con- 

 spicuous difference between the larva 1 of Ojihinru albidn, <if finis and Ic.rlurata 

 proves these forms not to be so very closely related, in spile of the fact 



