112 HERBERT E. DURHAM. 
8. It is the site (together with “ Tiedemann’s bodies,” 
“ Polian vesicles,” &c.) for the production of ameboid cor- 
puscles (vide Prouho, Cuénot, et alt.). In Asterids this func- 
tion is carried on all over the system, in Echinids it is limited 
» certain situations (dorsal organ, &c.). 
4. It has some concern with the working up of effete mate- 
rial. Some evidence has already been given (vide Hamann, 
Perrier, Koehler, &c.). Sarasin (19), from his study of Astheno- 
soma, considers the dorsal organ to be a typical nephridium 
with coelomic funnels, and communicating with the exterior 
through a canal (ureter) which opens in common with the 
water-tube at the madreporite. The morphological aspect of 
this idea will be considered below. The dorsal organ has been 
compared (supra) to the pericardial gland of molluscs (p. 33), 
with which organ it agrees in taking up carmine (Kowalewsky, 
No. 40). 
I would strongly insist, with Prouho (No. 11, p.336), that there 
is no communication between the cavities or lumina of the 
hzmal system itself with other spaces, which some authors 
have described, and which Shipley (No. 57) quotes. The com- 
municating cavities which they describe are hollowed out in 
the substance (inter-canalicular) of, e. g., the dorsal organ, but 
they are not in continuity with its hemal (intra-canalicular) 
channels. As Prouho remarks, the only methods of communi- 
cation between these hzmal channels and other spaces are (i) 
by osmosis, (ii) by diapedesis of corpuscles. 
The following method of regarding the relations of the water- 
tube, dorsal organ, axial (perihzmal) sinus, and the madre- 
transudation through a living membrane; otherwise it would appear para- 
doxical, if we accepted his theory, that non-dialysable egg-albumen when 
injected into the circulation should pass through the renal epithelium and 
appear in the urine as egg-albumen.- The presence of a living membrane 
appears to be sufficient to prevent any such loss of dialysable bodies, at any 
rate until our methods are adequately refined for testing the validity of his 
hypothesis. It is also interesting to note that (No. 8, p. 49) he can prove 
that certain granules do not consist of hemoglobin, although spectroscopically 
they appear identical with that substance, by means of a magnifying power of 
1500 diameters ! 
