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formation that has been given here of its larva is sufficient lo show lhal 

 it differs very markedly from the true Strongylocentrotus-larvx in its body 

 skeleton in the first stage forming a basket-structure: there is then very 

 good reason to expect that also in its second larval stage it will prove to 

 agree with the Toxopneustid larval type. At least the fads known are 

 decidedly not in favour of Clark's views. 



Regarding the genera referred by ('.lark lo the family Kchinomelrida- 

 there can be no doubt that they really form a natural group, I'aruxalenia 

 alone being doubtful. It must then be claimed that the larva? of these 

 forms should be in conformity with one another in their essential features. 

 It is a pity that we do not know much about these larva', only one species, 

 Echinumetra lucunler, having been reared to its lull larval shape and through 

 metamorphosis. Hut it is known lhal the larva' of Erhinnmclrn obloiu/(t and 

 Colobocentrotus utralus agree with the Ech. lucunter-larva in the very char- 

 acteristic feature of the recurrent rod being double, and it is highly prob- 

 able that the same character applies lo the larva- of Erhinomdm Mnlluvi 

 and Helerocentroliis mamilldlus. Thus Hie facts hitherto known regarding 

 the larva? of the Echinometri(Ue agree very well wilh the results derived 

 from the study of the adult forms as lo their natural affinities. 



Summarizing now the preceding discussion it must be staled lhal the 

 study of the larva 1 most decidedly lends support to the author's 

 views as lo the classif ica t ion of the Camarodonta, and thus also 

 gives proof of the correctness of ascribing c o m p a r a I i v e 1 y great 

 importance to the minor microscopical characters of pedicel- 

 laria 1 and spicules in Ihe classification of this group. The classi- 

 ficatory results reached on using these characters, combined with tin- 

 characters of the test, have been splendidly confirmed through the study 

 of the larva*. Disregarding these characters, Clark was led e. g. lo such 

 an absurdity as to include S^twrrcliitnis </r<nnil<iris in the genus Slroniiylo- 

 ccnlrotiis, otherwise so naturally circumscribed through Ihe peculiar char- 

 acter of its globiferous pedicellaria-. There is no reason lo enter here on 

 a discussion of Ihe objections raised especially by Clark against using 

 these microscopical characters in classification, as il may now be regarded 

 as an established fact that they are really of eminent elassificalory value. 

 Thereby I do nol mean lo maintain thai my classification was correct in 

 all details. Thus e.g. the position assigned b\ me to the genus SlmiHji/lu- 

 ccnlrolns, mainly on account of the structure of its globiferous pedicel- 

 laria 1 , as being probably related to the Toxopneuslida-. was evidently in- 

 correct. The study of the larva- shows lhal il is most likely lo be an oll'shoot 

 from Ihe Kchinida> s. sir. t'pon Ihe whole I would emphasi/e lhal Ihe Irue 

 position especially of the forms belonging lo the Camarodonla, (excepting 



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