PHYSIOLOGY AND PIOLOGY. 
Ech. 41 
Russo (6) gives a resume of the results of his investigations on the 
embryology of Amphiura squamata. It is impossible in this form to 
distinguish between mesoderm and mesenchyme in the sense of the 
Hertwigs. A table is given of the organs originating from the ecto- 
derm, mesoderm, and endoderm respectively. The formation is de- 
scribed of the water-vascular system, nervous system, skeleton,- muscles 
of peristome and arms, digestive tract, and bursrn. 
The author further describes the genital organs of Amphiura 
squamata. The so-called umbilical cord does not exist. The larva 
adheres to the wall of the bursae by means of its external membrane, 
and is nourished by the bursal epithelium, which breaks down to 
produce elements that penetrate into the stomach by contraction of 
the oesophagus. 
IV.— PHYSIOLOGY AND BIOLOGY. 
Cud not (1) discusses various points in the physiology and mode of 
life of Echinoderms. The anchors of Synapta serve for locomotion, and 
to enable the animal to adhere to foreign bodies (p. 354). The hooks of 
Ophiurids are also organs of adherence (p. 35G). The Cuvierian organs 
are organs of defence (pp. 372-374). The means of defence of the 
different Echinoderm classes are # discussed at length (pp. 375-383). The 
function of the ciliated funnels of Synapta is to keep the coelomic fluid 
in motion (p. 399). Nutrition of the various groups of Echinoderms 
(pp. 414-416). The sacculi of Crinoids are organs of reserve (p. 423). 
Respiration and excretion (pp. 427-441). Hydrostatic (pp. 441-445). 
The terminal tentacles are perhaps olfactory (p. 498). The otocysts of 
Synaptids and Elasipoda and the sphaeridia of Ecliinids are both probably 
organs of the sense of orientation (pp. 504-507). The papillae on the 
tentacles of Synapta are probably olfactory (p. 514). The Polian vesicle 
forms amibocytes for the water-vascular system, and also functions as a 
reservoir (p. 550). Tiedemann’s bodies and the so-called Polian vesicles of 
Ecliinids are lymphatic organs (pp. 552 & 554). The stone canal probably 
assists in the respiration and excretion of tho ovoid gland ; it would also 
maintain the turgescence of the water-vascular system, and perhaps is 
the means of maintaining the internal pressure during the expulsion of 
the genital products, e.g., in Urchins (pp. 562-568). 
CUKNOT (5) describes the following Protozoa parasitic in Echinoderms : 
— Infusoria : Uronema echini , Maupas, from the intestine of Strongy - 
locentrotus lividus ; Uronema digitiformis, Fabre-Domergue, commensal on 
the skin of Asterias glacialis ; Jlemispeira asteriasi, Fabre-Domergue, 
from the dermal branchiae of Asterias glacialis ; Licnophora auerbachii, 
Grabe, from various Echinoderms ; Cyclochcda asierisci } from the dermal 
branchim of Asterina gibbosa ; Cyclochcda oqdiiothrices, Fabre-Domergue, 
from Ophiothrix fragilis ; Trichodina synaptce, n. sp., from body cavity of 
Synapta . inheerens ; Trichodina antedonis, n. sp., commensal on Antedon 
rosacea ; Rhabdostyla arenasia } n. sp., commensal on the skin of Synapta 
