STUDIES IN SPICULE FORMATION. 547 
ainsi la forme de la fig. E [see my fig. 12], et ainsi de suite.” 
Hérouard, amongst other things, attributes the existence of 
the perforations in the plates to the presence of the cell-nuclei 
which, he says, prevents the deposit of lime in their immediate 
vicinity, and, to thoroughly round off his theory, he subse- 
quently enters into half a dozen other “ explanations ’’?— 
referring the primitive form of the spicule to the contractility 
of the body-wall, etc.—which I have not space to recount in, 
much less examine. What is to be said of the foregoing, 
which professes to be an account of actual facts, written by a 
capable observer? M. Hérouard tells us that if we take the 
more or less macerated stroma of the body-wall of C. planci 
and place it in “ carmin acetique,” “ nous voyons sous l’action 
du réactif, le corpuscule calcaire disparaitre et étre remplacé 
par un réseau hexagonal a peu prés régulier, coloré en rouge, 
et au centre de chacune des mailles de ce réseau, un noyau : 
ces noyaux occupant précisément la place ot se trouvaient 
primitivement les trous du corpuscule.” I can only say that 
T have followed M. Hérouard’s instructions, and cannot find a 
trace of “ un réseau hexagonal.””! In fact I must categorically 
deny the whole series of M. Hérouard’s statements. The 
spicule does not arise as a minute tetrahedron; there are 
rarely four cells in connection with the terminally bifurcated 
rod (the more usual number being two), and then they are 
not hexagonal in form; four newly-arrived cells do not 
recularly attach themselves to the spicule for its further 
growth, and however many cells may ultimately be associated 
with the spicule they have, by no means, that symmetrical 
disposition claimed for them by M. Hérouard. I once showed 
my preparations of Cucumarian spicules to a friend who, 
merely glancing down the microscope tube, immediately ex- 
claimed, “ Ah, I see, one cell in every hole.” I regret that 
M. Hérouard has chosen to adopt a like method of arriving 
1 All that is to be seen in a carefully decalcified body-wall of a Cucumarian 
are the globular scleroblasts in connection with the thin film of plasm (now 
rendered more visible) which covered the mass of the dissolved spicule, 
