108 HERBERT E. DURHAM. 
nicht farbten. Vielleicht waren es Aufblahungen der Cuti- 
cula.” They say nothing further about them. 
Similar dilatations are seen upon the gastric and other 
hemal strands, as well as coagulum in non-dilated parts. It 
seems likely that there must be some slight circulatory onward 
movement of the fluid, probably from the gut-wall where 
absorption is going on, along the gastric hemal strands to the 
dorsal organ, and then to the genital and other tracts. Witha 
view to observing whether any onward movement could be 
discerned with the dilatations, the whole madreporic interradius 
was rapidly removed from specimens, and then the wall of the 
dorsal perihemal sinus and the water-tube were carefully 
removed with fine scissors ; the resulting preparation, consist- 
ing of the dorsal organ slung by the skeletal tissues, was then 
put in a watch-glass with fluid under a low power. Such 
preparations were made in the morning and observed from 
time to time throughout the day. I was never able to discern 
any change in the position or appearance of the dilatations. 
Prouho (No. 11) very properly insists on the probability that 
circulation is carried on (in Echinids) chiefly by a vis a tergo 
through absorption from the intestinc. The preparation of my 
specimens entirely precluded any such factor, and therefore they 
do not seem to be of importance in their negative result. 
When the size of the individual tubes is considered it is not 
surprising that attempts to inject the system fail, and the 
dorsal perihemal sinus only becomes filled (vide Vogt and 
Jung, 6, p. 610), or that Cuénot’s endeavour to inject the 
gastric hemal tracts did not succeed (No. 4, p. 92). 
As far as I have been able to make out, all the cells of the 
organ are of a leucocytic nature; and as such they are irre- 
gular in form and place. Hamann (1) figures and describes a 
regular epithelium within and without the extensile mem- 
brane; I have not seen a condition so regularly arranged as his 
figure represents, even in specimens of A. rubens and Cri- 
brella ocellata (vel sanguinolenta) of 1—1'5 mm. in dia- 
meter (vide Hamann, woodcut, p. 54,‘ Die Asteriden’). From 
the irregularity in the disposition of the cells, as already 
