Slægten Flpidia maa efter vor Opfatning stilles nær- 
mest Kolga i den systematiske Række, men over denne. Vi 
kunne ikke være enige med Dr. Théel, der setter Elpidia 
meget høit, idet han udtrykker sig saaledes: “Cependant, 
d'aprés la description que jai Vhonneur de présenter å 
I Académie, il ressort quil se trouve å un degré de dével- 
oppement bien supérieur å celui de toutes les Holothuries 
connues jusquå présent, teémom en particulier la symétrie 
bilaterale sensiblement aceentuée chez lui.” 
Den bilaterale Form, der er temmelig stærk udpræget 
hos Elpidia og endnu skarpere hos Kolga, er det fornemmelig 
Théel lægger Vægten paa, naar han stiller Elpidia saa hoit 
i Udviklingsrækken; men ser man hen til, at en Mængde 
Echinodermlarver have en bilateral Form, og at denne f. 
Ex. hos Slægten Psolus ingenlunde har begrundet dennes 
systematiske Stillmg, saa kunne vi ikke medgive, at den 
bilaterale Form kan tynge stærkt i Vægtskaalen, hvor det 
gjælder Anordningen i Systemet. Her forekommer det os, 
at der maa tages væsentlig Hensyn til den hele Organisa- 
tion, og gjør man dette for Elpidias Vedkommende, saa 
viser det sig, at Huden visselig indeholder en stor Mengde 
Kalk; men Spikelformen er den mest fremtrædende; og de 
smaa Hjul, som foruden Spiklerne ere tilstede, tyde hen 
paa et svagt Slegtskabsforhold med Chirodoterné, temmelig 
lavtstaaende Holothurider. Det indre Skelet er jo bygget 
omtrent som hos Kolga, kun noget stærkere; men Spikel- 
dannelsen er der, og det er uskikket til Fæstepunkt for 
Længdemusklerne. Stenkanalen er med sin yderste Ende 
fastvoxen til Huden; men nogen udviklet Madreporplade 
findes ikke; kun der, hvor Sammenvoxningen finder Sted, 
altsaa paa Stenkanalens yderste (øverste) Ende, iagttages 
en Kalkfletning, der er Begyndelsen til en Madreporplade 
— et Skridt over Larvestadiet. Vandkarsystemet har kun 
to Ambulakralkar og Tarmkanalen intet Appendix (Lunger). 
Nervesystemet er som hos Kolga, kun er der langt færre 
Høreorganer, end hos denne. Alt dette tyder dog hen paa 
en lavere Organisation, end hos de fleste Holothurier. 
Slægten Jrpa har jo mange Berøringspunkter med 
baade Elpidia og Kolga, og kan ikke stilles synderlig høiere 
end disse; men den har dog Noget, der fjerner den lidt 
længere fra Larvestadiet, end de to nævnte, og det er, at 
«paa Stenkanalen, strax indenfor den Ende, der er fastvoxen 
til Huden, er en udviklet Madreporplade. 
20 
i 
auditory properties; for it is ‘hard to ¢onceive: that an 
animal ranking in other respects so low should be highly 
endowed in this. 
Elpidia must, we opine, in the systematic order of 
arrangement be placed next to Kolga, but next above that 
genus. We cannot agree with Dr. Théel in giving a high 
rank to Elpidia. He says in his Memoir: — “Cependant, 
d'aprés la description que j’ai Thonneur de présenter å 
VAcadémie, il ressort quiil se trouve å un degré de dével- 
oppement bien supérieur å celui. de toutes les Holothuries 
connues jusqu'å présent, témoin en particulier la symétrie 
bilaterale sensiblement accentuée chez lui.” 
The bilateral form, which is rather a prominent fea- 
ture in Elpidia, distinguishes in a still higher degree Kolga, 
and it is this character that has chiefly induced Dr. Théel 
. to give Elpidia so high:a grade in the scale of develop- 
ment; numbers of the larval forms of Echinodermata 
are bilateral, but this has not been the character — 
in ranking the genus Psolus for instance — determina- 
tive of systematic position; and hence we cannot con- 
cede that bilaterality of form should have any material 
influence thereupon. In arriving at such a decision, the 
organization as a whole should, in our opinion, be the 
chief criterion to be guided by; and assuming this to be 
the case, Hlpidia must descend to a lower status. It 
is true, the skin in this genus contains a very large 
amount of calcareous deposit, but the spicular form 
greatly predominates; and the rotated corpuscles, or wheels, - 
that occur along with the spiculæ, would seem to indicate 
a slender link of ‘connexion with the Ohirodotæ, rather low- 
graded Holothurians. The structure of the inner skeleton is 
much the same as in Kolga, only somewhat stronger; but 
here, too, the spicular formation constitutes a leading. fea- 
ture, and renders it of no service as a point of attachment 
for the longitudinal muscles. , The sand-canal is connate at 
its upper extremity with the integument, but there is no 
fully developed madreporie body; where the skin and the 
stem unite, however, at the upper extremity of the latter, 
occurs a calcareous web — the rudimentary indication of 
a madreporic body, showing the animal to rank a grade 
above the larval stage. The aquiferous system is furnished 
with two ambulacral vessels; the intestinal canal has 
no appendix (respiratory tubes). The nervous system is 
similar to that in Kolga, save in the number of auditory 
vesicles, which is far more limited. But, taken together, 
all these structural details assuredly point to a. lower orga- 
nization than is met with in most Holothurians. 
The genus /rpa presents numerous points of resem- 
blance to both Ælpidia and Kolga, and cannot be ranked 
much higher than the two latter genera in the scale of 
development; it has, however, a character removing it a 
step farther from the larval stage than is either of those 
animals, viz. a fully developed madreporic plate on the 
- sand-canal, in immediate proximity to the point at which 
the latter is connate with the skin. 
