324 
P. HERBERT CARPENTER. 
this view is based, or he would scarcely have written as 
follows (p. 317) : 
“ Der ganze Beweis fiir diese AuflFassung hegt darin, dass, wenn man von 
dem Mittelpunkt der dorsalen Oberflacbe des Thieres ausgeht, bei den 
Crinoideen die Basalia, bei den Ecliinoideen die Genitalia die ersten Platten 
sind, welcbe stets und immer in der Bicbtung der Interradien angeordnet 
sind. Irgend welcbe unmittelbaren Beziebungen zu den inneren Organen des 
Tbierkorpers sind bei dieser lediglicb auf die raumlicbe Auordnungsweise 
jener Platten gegrundeten Homologisirung nicbt in Betracbt gezogen 
worden.” 
The view attacked by Ludwig rests, however, on a much 
firmer foundation than the mere anatomical fact which he 
calls the ganze Beweis ” of its truth. The evidence of 
Echinoderm embryology is all in its favour ; but Ludwig 
does not make the slightest mention of this evidence, much 
less attempt to controvert it. 
It is as follows : — The interradial abactinal plates (basals) 
of Crinoids are developed with precisely the same relation to 
the vaso-peritoneal apparatus of the larva as are the inter- 
radial abactinal plates (genitals) of Urchins and Starfishes. 
In both cases these plates first appear in the form of a spiral 
around the right peritoneal vesicle (Agassiz, Gotte) ; but 
the orals of the Crinoids, which Ludwig considers homo- 
logous with the genitals of Urchins and Starfishes, are 
developed spirally round the left peritoneal vesicle (Gotte). 
Are not these peritoneal vesicles as "important inner organs’^ 
as any in the whole morphology of the Echinoderms ? 
They develop before the water-vascular apparatus, on the 
connection of which with certain plates of the adult, 
Ludwig lays such stress. 
He admits that the oral or actinal side is homologous in 
all Echinoderms as being chiefly developed from the left 
side of the larva ; and yet he considers plates developed on 
the left or actinal side of one Pluteus larva (Ophiurids) as 
undoubtedly homologous with those developed on the right 
or abactinal side of another (Echinids), and leaves the 
abactinal plates of the Ophiurids (genitals) out of consi- 
deration altogether. 
It seems to me that he assumes too much in regarding 
the water-pore of the adult as a fixed point. If he could 
show that one of the genitals of an Urchin or Starfish larva 
were primitively perforated by the water-pore as is one of 
the orals of a larval Crinoid, then his position would be 
strong indeed. But this is very far from being the case, 
lie admits himself that in young Starfishes (Loven) there is 
no connection between the water-tube and any genital plate. 
