202 



the genera SpaUtnfiiis, Echinucardium, Moirii, Brissus, Brissopsis, Meoma, 

 and besides a niunl)er of other Spalangoid-larva' (luhinoplulciis fusus,soli- 

 dus and otliers) are known to exist. They all of Iheni agree in having the 

 un|)aired i)osterior |)rocess. and there is not the shgiitest reason to expect 

 that there will he any exception to this nile. We have then here a 

 larval lype c()rres|)()nd i ng to the order of I h c Spa I a ngoi dea, 

 forming a distinct larval "Order." 



is it ])ossible to distingnish larval iainilies'" williin this order, corres- 

 ponding to the families of the adnlt SpalangoidsV \\\' are not yet in pos- 

 session of sufficient facts for answering this question definitely : but the 

 facts which are known would seem to point in the direction that also 

 "families" may be distinguished within this larval order. 



The S|)atangoi(l-larva^ may be divided into two main groups, viz. 

 liiose with |)()slei()laleral arms and those without. Of the latter group 

 only one species has been referred to its j)arental form, viz. that of 

 Brissopsis lijiifero; but there is some reason to suggest that also the 

 larvae of the genus Brissus belong to this lype (comp. above, suh Brissus 

 Agassizi, p. 119). .\ larva of the same type, which was found in the 

 (iulf of Panama I would be incUned to refer to Meonui (/randis. That 

 would tend to indicate that this larval type is characteristic of the family 

 of the Brissida. Hut it can be nothing more than a suggestion at the 

 present state of our knowledge; moreover the fact that Metschnikof f') 

 has found a larva of this type occurring in great numbers at Triest, where 

 Brissus unicolor, otherwise common in the Mediterranean, ai)parenlly 

 does not occur, would seem to prove that this larval type may also be 

 found in other Spatangoids. Metschnikoff refers this larva to Schizasler 

 cuualiferus "da sie dort unter den Echinoidenlarven ebenso vorherrschend 

 ist, wie Schizaster unter den erwachsenen Spatangoiden." 



The larvae of the genera Echinocardiuni, Spatanf/us and, probably, 

 Moira'^) agree in having posterolateral anus, supported by a simple rod, 

 not widened at the base. This would point in the direction of this larval 

 type being characteristic of one group of Spatangoids. The existence of 

 several species of the type of Echinopluleus fusus might indicate that this 



■) E. Metschnikoff. ■■.Stiulieii iiber die Iintwickeliing d. Eeliinodernicn u. Nemertinen." 

 M^m. Acad. St. Pelersbourg. VII. Ser. XIV. 186i). p. 46. Taf. VIII— IX. 



^) Caswell Grave has reared the larva of Moira alropos through metamorphosis, but 

 unfortunately does not give any iidorniation of the shape of the larva. On my applying 

 to him lor the information wanted, he kindly sent me some slides containing some of the 

 larva'. It turned out, however, that there were two dilTerenl species of larva- in the slides, 

 one with posterolateral arms, the otlier without. Having called his attention to this fact 

 I was informed by him that lie thought it almost certain that the form with the postero- 

 lateral arms was the iUo/ra-larva. but full certainty could not be obtained any more from 

 the material still preserved. 



