148 W. WOODLAND. 
ments: (a) the tylostyle spicule arises by the fusion of 
separate granules present in the substance of the mother- 
scleroblast ; (6) the chiaster spicule arises by the junction at 
their inner extremities of several rods of silica which are 
deposited in the scleroblast so as to lie radially in the cell- 
sphere; and (c) the spheraster usually arises by the fusion of 
two or more calthrops (each of which arose as a granule con- 
tained by a single scleroblast), which serve as a basis on 
which the rest of the silica is deposited—from which it is 
inferred that Tethya has tetractinellid affinities. This last 
statement is illustrated by a somewhat extraordinary figure 
(his fig. 35) of two closely-apposed attenuated calthrops 
spicules, each contained in its scleroblast. It is significant 
that if these three statements be true, then, as before stated, 
spicule formation in Tethya lyneurium proceeds in a 
manner different from that hitherto found in any other 
monactinellid, or, for that matter, tetraxonid sponge. 
With regard to the first statement, I entirely agree with 
Weltner’s estimate of its value (88). Weltner rightly con- 
siders that the several granules have nothing to do with the 
tylostyle spicule, and that this arises, like other siliceous 
monaxons, from a single granule which gradually elongates 
and assumes the form of the adult spicule by continued 
deposition of silica on its surface. Further Maas’ figures of 
vided that plenty of suitable material, i.e. a quantity of very young Sycons, is 
to hand, that this material is prepared in the way described by Minchin, and 
that the observer possesses sufficient patience to find the comparatively few 
young stages in his preparations. Maas’ remarks about what he supposes to 
be my ignorance of his own paper and other relevant literature are incompre- 
hensible to me since, besides being entirely mistaken, they are entirely irre- 
levant to the subject under discussion. Because, as Maas points out, I 
adopted Minchin’s convenient summary (‘Zoological Record’ for 1901) of 
his statements concerning spicule formation (and Maas does not dispute the 
accuracy of Minchin’s rendering of his statements) I fail to see that anyone 
is justified in drawing the curious conclusion that I was unacquainted 
with the paper which I was criticising! I may add that in my previous 
paper (5) I inadvertently ascribed “ tuning-fork ” spicules to Clathrina 
lacunosa. . 
