30 MIDLAND NATURALIST. 
work of the Zoologist, the important thing in a man’s library is not 
where his books are placed—provided he knows what they contain. 
It would be loss of time for me to enter here upon a discussion of 
the various systems of classification with reference to the Porifera, 
whether it should be natural or artificial; phylogenetic or morpho- . 
logical is of no consequence for the moment. ‘Those of my readers 
that want this kind of thing can find it in the classical works of 
Bowerbank, Oscar Schmidt, Zittel, Gray, Carter, Heckel and 
Vosmaer. For my part I believe that Professor James Hornell, of 
the Jersey Marine Biological Station, has chosen the: form of classi- 
fication best adapted to my purpose: In Vol. I., No. 2, February, 
1894, of ‘‘The Journal of Marine Zoology and Microscopy’’ page 
39, he formulated the following system : y 
PHYLUM : — PORIFERA. 
Branch A, Calcarea Branch B, Non-Calcarea 
Family I.—Asconidae. . Class I.—(Skeleton siliceous) 
'"  II.—Syconidae. Silicispongiae. 
“ooo, HT. —Leuconidae. ; Order I.—Monaxonida. 
(Characterized respectively by the “ II.— Tetractinellida. 
Canal system indicated by '* III.—Hexactinellida. 
the name. ) Class II.— (Skeleton fibrous) 
Ceratosa. 
Class III.—(Skeleton none) 
Myxospongiae. 
The Calcarea are recognized by the chemical composition of 
their so-called skeleton. This skeleton is in the form of needles and 
spines of various forms, but invariably their animal matter is highly 
or almost completely impregnated with calcium carbonate, and can 
easily be verified by subjecting them to any mineral acid, which 
wil disolve them with effervescence. They are all marine and 
therefore do not concern us in this study. 
'The non- Calcarea include, as may be seen from the table above, 
three kinds or classes. In the fizst class are included all sponges 
that have spicules of a siliceous or glassy composition. In the 
second, we find those sponges whose skeleton consists of a horny. 
fibrous network, (sponge of commerce ), and the third class includes 
those that have no skeleton and wholly consist of soft animal matter. 
: The reader will notice that the siliceous sponges are sub-divided 
into three orders and these orders are again based onthe form of 
_ the spicules. In the first order the glassy needles are simple rods 
. or needles. In the second the spicules consist of four needles 
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