0 Spong . spong le. 
can be practically applied to Calcarea. Each Sponge is to be looked upon 
as an individual, whether it be a “ person ” or a “ stock.” 
For the phylogenetic relations of the families, subfamilies, and genera 
of Calcarea , with diagrams, see pp. 420-423. For a new nomenclature 
of the rays of the tetractine spicules, see p. 187. 
von Lendenfeld (2) describes the arrangement of the siliceous 
spicules in the species of Geodia occurring in tho Adriatic, and finds in it 
a new proof of the correctness of F. E. Schulze’s theory of the origin of 
the different forms of spicules. 
Rauff (1) describes (i) the skeleton of the Anomocladina , and (n) 
a Sycon-like group of fossil Calcarea, which he terms Polysteganin.ee ; — 
r. The fundamental form of the Anomoclad skeleton is the tetraxon. 
It is nearest related to the tetraclad spicule, being a regular 4-rayed 
element, with one arm shortened and differentiated in form. The author 
terms this arm the “ Knoten ” (knob) ; it is usually thickened or swollen. 
The skeletal elements are united in such a way that the ends of the 
normal arms are applied to the “Knoten” of neighbouring spicules. All 
spicules are so placed in the Sponge body that the “ Knoten ” are directed 
centrifugally outwards. Two groups can be distinguished by the position 
of the spicules. In the first group (e.g., Astylospongki) all the spicules 
have (theoretically) one and the same position, so that their correspond- 
ing limbs are parallel to one another, and similarly orientated. As a 
result, in each “ Knoten” four spicules fuse with one another, namely the 
one to which the “ Knoten ” belongs, and three others, and the meshes of 
the skeleton are similar and contiguous rhombohedra. But a complica- 
tion is always introduced by the fact that the normal, primary, or principal 
arms, as they may be termed, send out secondary arms, which resemble 
the primary ones. The points of bifurcation generally lie close to the 
“ Knoten.” The secondary arms attach themselves to neighbouring 
“ Knoten,” and the three include between them an angle of 90°. In the 
second group ( e.g ., Hindia) secondary arms are wanting, and the spicules 
have not all the same position, but usually two kinds of positions, in 
which neighbouring spicules alternate. The one position arises from the 
other by revolution of the spicule through 00° round the axis of the 
“ Knoten ” Then the “ Knoten ” lie in the edges, and the arms in the 
surfaces, of hexagonal tubes. In tetraclads also a definite plan of struc- 
ture could be determined, but not universally demonstrated. The 
tetraxons, touching one another with the ends of their four equally- 
developed arms, take such a position as to enclose regular rhombic dodeca- 
hedra, the edges of which are formed by the arms, the middle points of 
the spicules lying in the trigonal corners. 
ii. Fossil Calcarea do not differ in any essential way from recent forms. 
The fundamental skeletal element for all Calcarea , Triassic forms included, 
is the triradiate spicule. The so-called Pharetron-fibre is a secondary 
phenomenon, due to fossilization, and the spicules were not originally 
united by spongin or other cementing material. The Polysteganince arc 
a new group of Sycons, only differing from recent Sycons by a peculiar 
