132 SVKN LOVEN, ON THE ECHINOIDEA BESCRIBED BY LINN^US. 



strueture neailv similar in botli, seem to be made subservient 

 to a similar funetion, different from that of the ventral pedi- 

 cels, apparently that of respiration, but with his incomparable 

 keenness of observation and ahvays ready power of reflection, 

 it may well be that wheu he liad come to observe that the 

 mamelons of the Diadem atid;e are perforated like those of the 

 Spatangidfe, he looked aboixt for other resemblances and was 

 led to surmise a relation of homoloo-y betweeu the eonvex, 

 dorsally expanding and laneeolate ambulacra of the Echinns 

 Diadema, and the xradii eoneavi a centro deducti, lanceolati» 

 of the E. Spatagus, and, in recording his conception of the close 

 affinity between the two Diaderaatid;ie, purposely iised for these 

 the terms »radii > >-puneta perforata^ and »centrum^, elsewhere 

 chosen for the Spatangi and other Irregnlares, and, as au in- 

 nuendo of some distant eonnexion betAveen the two groups 

 to be taken into consideration on some futiire day, fraraed his 

 remarks after the Spatangean model, »ut vel alirpialis horum 

 sxiperesset idea». 



The referenccs to preceeding aiithors attaehed to these 

 two speeies are sueh as fully to bear out the expedience of 

 attending principally and above all to the descriptions of LiN- 

 N.«us, properly understood, and to look with donbt upon the 

 ((notations even as subsidiary means for determining his speeies. 

 It must be kept in mind that in 1758, wlien adding new re- 

 ferences, he was guided solelv bv the reeollection of the spe- 

 cimens he had seen in 1752, six years before. In the Lectures 

 of that year no quotation is given under the E. Diadema, 

 tmd under the Echinus saxatilis only liUMVHius, t. 14, f. ^-1. 

 As said already, this (igure eannot have been eited but witli 

 regard to the size and to the disposition of tlie zome; in other 

 respects it is too defieient, it docs not show tlie depression 

 of the centrum particularly laid stress upon, nor tlie perfora- 

 tion of the vcrrue;v\ Schynvoet, the editor of the IJariteit- 

 Kammer, says in the note on p. o2: »The Eehinus saxatilis 

 stånds upon t. XI \', lig. A, tliough somewhat smaller (»docli 

 wat kleinder») to whieli I have added one of the sort ealled 

 with US the Turkisli Turban, []<>•. B, verv rare, both toi>ether 

 communicated by Dr d'Acquet . Schynvoet. it appears, eould 

 not make out tlie Eehinus saxatilis of HiMfHius, of Avhif?li 

 there existed no authentical s])eeimen, and of whicli thcrc was 



