398 * THE VOYAGE OF H.M.S. CHALLENGER. 
Echinoderm, which seems to be inseparable from Lovén’s use of the term. Should Prof. 
Lovén ever write anything more upon the apical system of Echinoderms, he cannot avoid 
referring to the radial plates between the dorsocentral and the so called genitals (costals 
or basals) of an Asterid. He cannot speak of them by the name which was given them 
by Sladen who discovered them, viz., ‘ under-basals,” for this term would be meaning- 
less and confusing unless the plates outside them (the costals of Lovén) were also called - 
basals ; and he would therefore have to invent a new name for them, a proceeding to 
which he objects, or else adopt the terminology of Sladen and myself. I am sanguine 
enough to hope, not only that this will be the case, but also that the presence in Asterids 
and Ophiurids of plates homologous with the under-basals of Crinoids will lead him to 
abandon his theory of the homology of these under-basals with the dorsocentral of an 
Urchin or Starfish. I little expected six years ago to get so complete a confirmation of 
the views I then expressed as the presence of a “ dicyclic base” in several Asterids and 
Ophiurids as well as in Cyathocrinus and Marsupites. The similarity “in structure of 
the apical system in all the groups of brachiate Echinoderms thus becomes exceedingly 
striking; and it affords a further proof (if such were needed) of the homology between 
the apical systems of the Echinozoa and the Pelmatozoa respectively. 
Two authors, however, have been led to an entirely different conclusion respecting 
the interradial abactinal plates of the Starfish larva from that of Lovén, Agassiz, Sladen, 
and myself. Ludwig regards them as homologous with the orals of a Crinoid, because 
one of the latter is pierced by the primitive water-tube;* while the madreporite of an 
adult Starfish is in relation with one of the so called genital plates (costals or basals). 
The morphological difficulties inseparable from this inversion of the relations between a 
Starfish and a Crinoid, as ordinarily conceived, have been discussed by Sladen? and 
myself.* With the exception of Studer,‘ whose errors have been discussed elsewhere,* no 
other writer has alluded to the subject; though it has recently made its appearanee in a 
somewhat modified form. Perrier stated two years ago ° that the primary interradial plates 
around the dorsocentral of the young Brisinga develop into the so called odontophores 
of the adult. The former are the plates which are usually known as the genitals (costals 
of Lovén; basals of Sladen and myself); and if Perrier’s statement be correct, the views 
of Lovén, Agassiz, Sladen, and myself respecting the homology of the apical plates 
through the whole group of Echinoderms are no longer tenable. No proofs of it have yet 
been offered, however, though in a later note by Perrier’ the following passage appears, 
“Les jeunes Astéries, les jeunes Brisinga présentent aussi, comme Lovén et nous-méme 
1 Zeitschr. f. wiss. Zool. Bd. xxxiv. p. 318, 1880. 
2 Quart. Journ. Micr, Sci., 1884, vol. xxiv., N. S., pp. 35-40. 
3 Ibid., 1880, vol. xx., N. S., pp. 322-329. 
* Uebersicht tber die Ophiuriden welche wihrend der Reise S.M.S. “Gazelle” um die Erde, 1874-76, gesammelt 
wurden, Abhandl. d. k. Akad. d. Wiss. Berlin, aus dem Jahre 1882, Phys. Kl. Abh., i. p. 10. 
5 Quart. Journ. Mier. Sci., 1884, vol. xxiv., N. S., pp. 15-18. 
® Note sur les Brisinga, Comptes rendus, t. xev., 1882, p. 63. 7 Ibid., p. 1381. 
i. 
