ON WANDERING CELLS IN ECHINODERMS. 113 
poric or water pores, has, I believe, never been formulated; 
it has the advantage of bringing the different arrangements 
which have been described into harmony, and will put an end 
to the battles which have been fought over the point. 
First of all we must refer to Bury’s (No. 16) discovery, that 
the central water vascular apparatus is developed in three 
pieces—(i) the water-tube, (ii) an ampulla of anterior entero- 
cele, (iii) the water-pore. He further promises to prove 
(p. 443) that the left anterior enterocele becomes the so-called 
**schlauchformiger Kanal” (what is here termed the axial 
perihzmal sinus). 
In specimens of Cribrella, 2 mm. in diameter, I find that 
there is as yet but a single water-pore, which communicates 
with the cavity of the axial sinus ; into the latter the free end 
of the water-tube opens; thus these three spaces are in com- 
munication with one another at a comparatively early period. 
Now this free communication may remain throughout life 
in many forms, as Cuénot (No. 4, p. 92) proves :— J’ai 
constaté par les coupes que des canaux madréporiques dé- 
bouchent directement dans le sinus axial chez l’Echinaster 
sepositus, divers Astropecten, la Liudia iliaris, l’As- 
terias glacialis, et l’Asterina gibbosa; chez les grandes 
espéces, Asterias glacialis et Astropecten aurantiacus, 
on peut, par l’injection et la dissection, trouver les orifices sans 
faire de coupes. On voit que le fait est parfaitement constant 
dans toutes les familles,’” and as I showed in Cribrella 
oculata (‘ Proc. Roy. Soc.,’ vol. xliii, p. 330). 
Now the cavity of the axial sinus extends amongst the 
strands which form the dorsal organ; these spaces we will 
term intercanalicular, as distinguished from the intra- 
canalicular, which are the actual cavities of the strands 
themselves ; and between these there is no free communication, 
as has already been stated. 
In the dorsal organ of Echinids there exist epithelium-lined 
cavities which communicate together, and with a cavity 
extending longitudinally along the organ; this is termed the 
“canal aquifére annexe” by Prouho (No. 11), and the spaces 
VOL. XXXIII, PART 1,—NEW SER. H 
