14 PROF. E, A, MINCHIN ON THE [May 2, 
all of small size. The big, spreading colonies of contorta always 
have monaxons. It is my belief that the absence of monaxons is 
simply a juvenile feature, so to speak, of the sponge, and that they 
are only formed when the sponge has grown to a certain size. 
Such changes of spiculation with age are probably more frequent 
in sponges than is usually supposed. Fora parallel case I need 
only refer to Topsent’s observations on Cliona celata. 
A point which requires brief discussion, however, is why 
Lendenfeld found only the spinosa-form in the Adriatic, and not the 
contorta-form, if these two forms are really only age-variations in 
one species. Are we to suppose that in the Adriatic the sponge 
does not acquire monaxons? In my opinion the explanation of 
this point is to be sought in quite a different manner. In his 
‘ Kalkschwiimme der Adria’ [3] Lendenfeld describes another 
species of Clathrina occurring commonly in the Adriatic, namely 
C. reticulum. I have also found this species very abundant at 
Banyuls, and I possess many specimens of it; but my experience 
of this species at Banyuls differs sharply in one respect from 
Lendenfeld’s observations upon it in the Adriatic. I find reticulum 
to be more constant in external form and characters than any 
other species of Ascon. All the specimens I have seen—and at 
one time I had some hundreds of specimens, collected in order to 
obtain the larval development—are compact, rounded, cushion- 
like masses of slender, closely-knit tubes, forming a dense and 
finely-meshed reticulum from which arise one or more oscular 
tubes of much larger calibre than the tubes forming the body of 
the sponge. I have figured such a specimen elsewhere (4, p. 6, 
fig. 6). In short I have never had the slightest difficulty in 
recognising reticulum at sight, though its spiculation often 
approaches that of contorta very closely. My astonishment was 
therefore great to find that Lendenfeld describes this sponge as 
occurring (at Sebenica and Lessina) in nearly all the forms generally 
found in Ascons. There is thus a great discrepancy between Len- 
denfeld’s observations and mine with regard to this species,and I am 
inclined to think that this is to be explained simply by Lenden- 
feld not having recognised the true contorta, but having confused 
it with reticulum. This is a supposition which I am unable to 
prove or test; but if correct, it would explain why Lendenfeld 
did not find the true contorta occurring in the Adriatic as well as 
spinosa, and also why he finds vedtiewlwm so variable in form when 
in my experience it is so extremely constant. I may add, finally, 
that the figures of monaxons of reticulum given by Lendenfeld 
(3, pl. viii. figg. 7 e-7f) are more like those of contorta than those 
of reticulum, though not exactly like those of either, as these 
sponges are known to me. 
I will now describe some of the historically important specimens 
to which I have had access, and I begin with the type-specimens 
of Bowerbank’s Leucosolenia contorta in the British Museum 
(Bowerbank Coll. 988). The “type” consists of seven dried 
specimens, all very small, stuck on a card, The largest specimen, 
