Knowledge of the Spongida. 255 
dently of its elasticity; while of its composition Schulze 
states: —“ Die Priifung auf Cellulose mit Kupferoxydammoniak 
sowie mit Schwefelsiure und Jod ergab ein negatives Resul- 
tat” (No. 27, p. 19, Sep.-Abd.). 
It is not confined to the Carnosa, although most abundant 
there; for it may be found more or less present in most sponges 
with and without the genuine dendriform fibre-skeleton ; 
although, where the latter is absent, this elastic tissue seems 
to supply its place. Perhaps the effect of its entire absence 
is best seen in the Calcispongie, where, in consequence of 
this absence, the fragility after drying is so great that the 
more tender forms, ex. gr. Clathrina, will hardly bear handling 
without breakage. 
How far, then, the presence or absence of the Elastic 
Tissue should influence our classification is the next point to 
be determined. 
It may be remembered that my diagnosis of the order 
Carnosa is simply ‘without evident skeleton ;” but to what 
extent this will suffice may be inferred from the facts that 
Chondrosia reniformis and falichondria suberea, Johnston 
(No. 2, pp. 140, 197), = Suberites domuncula, Sdt., both come 
under this definition ; for neither have an evident skeleton 
(that is, genuine dendriform anastomosing fibre), while Chon- 
drosta reniformis presents the consistence of india-rubber, and 
Halichondria suberea that of crumb of bread. Hence the 
former has been placed in the order Carnosa, and the latter in 
that of the Holorhaphidota. 
Now, as it is plain that Chondrosia reniformis possesses an 
abundance of the “ elastic tissue,” and Halichondria suberea 
scarcely any (if any), while both are equally “ without evident 
skeleton,” which is our present definition of the order Carnosa, 
it is evident that this definition alone is not sufficient. 
Again, when the “ elastic tissue ”’ is ever so scantily deve- 
loped in the dermal layer, the latter, however thin, as in 
Grayella cyathophora (Rio. 11), presents a gelatinous consis- 
tence, with slimy, slippery surface, rendered opaque by spirit 
of wine—which, while preeminently characteristic of the 
Carnosa, is, on the contrary, very different from the thin 
delicate transparent sarcodic film which characterizes the 
other orders. Hence it becomes necessary to add these points 
to our present definition of the Carnosa, which would then 
stand thus:—‘‘ Surface slimy, glutinous, without evident 
skeleton, more or less composed of elastic tissue.” 
Still there remains a little difficulty, as with all border- 
questions, in adjustment ; for in Donatia (Tethya) lyncurium, 
after which I have proposed a group, viz. Donatina, in the 
