438 
ECHINODERMATA. 
24. Troschel, F. II . Die Familie der Echinocidariden. Arch, 
f. Nat. xxxviii. pp. 293-356. 
Anatomy, 
Greefp(11 3 see also Zool. Rec. viii.'p. 4C2) has given some short contribu- 
tions to the more delicate anatomy of Echinoderms, especially of the Starfishes. 
Tie discusses: — the structure of the eyes (no lenses I), and the existence of a 
hitherto overlooked tentaculiform organ of sensation, connected with the eye, 
in Starfishes j their nervous and vascular systems (the cavity of the body, the 
anal and oral vascular rings, and the veins in the interior [!] of the nerve- 
stems) and organs of respiration (dermal tentacula and a peculiar hitherto 
overlooked gill-like [?] organ connected with the stone-channel and the anal 
ring) ; the dermal vascular system and the connexion between the difterent 
vascular and nervous rings j the so- termed intestinal veins ” of Tiedemann, 
which are shown not to exist j the madreporic plate, as conducting sea-water 
not only into the aquiferous system, but also into the true blood-vessels and 
into the cavity of the body j the multiplicity of the ‘^heart” and stone-channel 
accompanying that of the madreporic plate j the vessels that spring from the 
anal ring and enclose the organs of generation ; the communication established 
through the generative orifices between the vascular system and the sea- 
water } the peculiar (gill-like ?) structure of the anal ring j the nerve-trunks 
in Ilolothurians and the homology of their enclosing cavities with the ambu- 
1 acral furrows of Starfislies. 
Baudelot (3) discusses previous investigations on the nervous system of 
Echinoderms, demonstrating the nervous system in Ophiuroids and Echinoids 
treated with diluted acid, and entirely confirming the observations of Krohn 
on the latter. Tie describes the fibrillated and celluligerous structure of the 
nervous trunks, pointing out that the same structme is observed in the cen- 
tral fibrous cords of the arms of Antedon, which evidently do not belong 
to the nervous system. This he failed altogether to discover in the true 
Starfishes. 
Loven (14) has discovered an organ of sense (? of taste), the sphceridiaj' 
in the JEchinid<^, where they are placed, in difterent numbers, on the adoral 
parts of the ambulacra, in some in peculiar cavities of the test, in others on its 
surface their numbers and position in the different genera is given {Cidaris 
is the only genus in which they are not found) j they are small, movable, 
globular or oblong, stalked, calcareous, vitreous bodies, with a ciliated cuticle. 
Length OTl-0-375 millim. 
Spontaneous Division in Echinoderms. 
Lutken (15) records Starfishes and Ophiurans in which phenomena, ap- 
parently only to be explained by spontaneous division, have been observed, 
viz. several species of Ophiothela and Ophiactis, in which the normal number 
of arms is 6, and which are often found in halves, with 3 (rarely 4 or 2) arms, 
or with the representatives of the wanting anns in a more or less advanced 
state of reconstruction j and also Ophiocoma purnila (and allied species), in 
which, however, the fissiparity is restricted to the young, mature specimens 
being always regularly 6-armed. The same phenomena occur in Astenas 
problem^ and tenuispina (probably also in some closely allied species with more 
