«Loin d'etre nuisible aux vrais progres de la science, 

 cette multiplication des genres, lorsqu'ils sunt etablis sni- 

 des caracteres precis, ne saurait avoir d' autre effet que de 

 rapprocher de plus en plus les especes, que leurs caracteres 

 naturels Kent lc plus 6troitement Cest la le grand avantage 

 ilcs petits genres, et cet avantage est surtout sensible dans 

 les families, dont toutes les especes se ressemblent par leur 

 aspect cxtcricur et par l'ensemble de leurs caracteres. 



L. Agassis. 



On generic and specific Characters in the Echinoids. 



Everybody who has studied Echinoids, will have felt a considerable difficulty in recognising many 

 of the genera, at all events of the regular Echinoids. Such was, at any rate, my case at the commen- 

 cement of my researches. I studied the excellent collection of these animals found in our museum, 

 and found it to be more and more hopeless. A great many genera were exhibited, as: Echinus, 

 PsammecAmits, Toxopneustes, Hipponoc, Bolctia, Psilechinus, Lytcchimis, Loxechintts, etc.; but it seemed 

 to be impossible to discover the characters on which they were established, whether the naked tests, 

 or specimens that had kept the spines, were examined. And the literature did not contribute very 

 much to clear up the question. To be sure, some of these names (— as it will be seen, partly 

 unjustly — ) appeared to be synonyms; but nevertheless the other genera were not much better 

 characterized. We learned through long descriptions that the spines were thick or thin, few and scat- 

 tered, or many and closely packed; that the tubercles might be small or large, and that they might 

 be placed in more or less regular series, etc. — altogether things easily enough seen, but so relative, 

 that it was impossible to get any any firm hold. It was almost enough to drive one to despair. 



Still a faint hope was left. Might not the difficulty be in the literature, and the animals them- 

 selves in reality be less intractable? A profound and careful attempt at penetrating into the mysteries 

 of the relationship of the Echinoids was planned, and the plan was the simple, but clear one: to let 

 literature alone for the present, while the animals were studied thoroughly. Everything had to be 

 examined that might in any way be supposed to show systematic characters: the test, the spines, 

 the tube-feet, the pedieellariae, the spicules, the sphseridia?, etc. The beginning was to be made 

 with the Echimts-species. This choice seemed to be the best one, as these species have hitherto been 

 especially notorious for their difficulty, and a very rich material of them is found in the museum of 

 Copenhagen. The result was excellent. The animals proved to be very tractable, the species to be 

 very well characterized (with a few exceptions). The difficulties arise from the literature containing 

 numberless bad descriptions. And what a confusion is reigning in the literature with regard to 

 the names. Almost every species must drag along with it a lot of synonyms, not only specific syno- 

 nyms, but also generic ones. Several species have by and by been referred to a whole series of different 

 genera, to end at last as a separate genus, as badly characterized as most of the other genera. To 

 name only one instance: The genuine Psam/ucchinus-species: variegatus (Lamk.) and semituberculatus 

 (Val.) have by and by been referred to the following genera: Echinus, Lytechinus, Schizeckinus, Toxo- 

 pneustes, but only rarely, in recent times not at all, to the genus to which they decidedly belong. 

 On the other hand the following extraneous species have been referred to Psammechinus: Echinus 

 norvegiens, magcllanicns, miliaris, microtuberculatus, angnlosus, Strongylocciitrntns Gaimardi\ intermedins, 



