ECHINODERMATA. 
329 
Asteronyx Loveni, which has no branched arms, bears one madrepore- 
form plate on the abdominal surface, and is covered with prickle-like 
papillae on the margin of the mouth. Next follows the genus Trichaster, 
Agas., with one species, the arms of which branch regularly dichotomously 
towards the end, the madrepore-form plate is wanting, and the margins 
of the mouth are set with cylindrical papillae. The genus Astrophyton, 
with eight species, is the last ; its arms are branched from the base, the 
margins of the mouth seem set with spine-like papillae, and there is one 
madrepore-form plate. In an appendix to this work, anatomical distinc- 
tions of the families and genera of the Aste^^iix, and various other remarks 
on the internal structure of these JEchinodermata are communicated. 
Erdl has subjected the tentacles of the Asteriw and Ophiurce to a 
more exact investigation (Arch. 1842, i. p. 58). 
Kroyer (Isis, 1842, p. 932) confirms the opinion of MiiUer and Tro- 
schel (Arch. 1840, i. p. 329), that the small individuals, of two lines in 
size, of the Ophionyx armata, are only the young state of another Ophm- 
rid(E, probably of an Ophiolepis which he calls O. aculeata. This must 
in its growth gradually lose, from the basis of the arms to the point, the 
echinulated spines and double hooks which distinguishes the genus Ophi- 
onyx. Kroyer saw, in a specimen of this Ophiolepis aculeata, one-sixth 
of an inch in size, spines which were smooth, except at the extreme st 
joints of the arms, where some scattered echinulated spines and double 
hooks were present. He also observed an individual in the act of repro- 
ducing a lost arm, which had quite the construction of Ophionyx armata. 
Muller and Troschel, however, have placed Ophionyx armata in the 
family of the Asteriadce, as an independent species. Kroyer found, be- 
sides, in a Euryale ( Astrophyton ) verrucosa, two young Euryales (Isis, 
1842, p. 935), the smaller of which was only 9'" long, and from the man- 
ner of the branching of the arms, it would be considered a Trichaster, 
M. and T. ; but the larger one, in this respect, was already much nearer 
the mother. Kroyer concludes from this, that the different manner in 
which the arms branch in the Euryalae is not alone sufficient for found- 
ing new genera ; but Muller and Trochel have taken into consideration 
other essential characteristics in establishing their genus Trichaster. 
Sars has made the observation (Mull. Arch. 1842, p. 330), that Aste- 
rias sanguinolenta and angulosa, by a voluntary bending in of the basis 
of their rays, can form a well-closed cavity, in which the eggs are pre- 
served, and the young harboured for a long while. They hold fast to 
this cavity by their four clasping organs, and are carried about by the 
mother. 
The separate sexes of the Asterice and Ophiurce have been pointed 
out by Kolliker (Beitrage, op. cit. p. 39), and Rathke (Fror. Neue Notiz. 
No. 269, p. 65). 
Muller has undertaken a work on the genera and species of the 
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