6 
PACIFIC SCIENCE, Vol. IV, January, 1950 
hypochlorite solution on the sample, add a 
cover slip and study, pressing on the cover 
slip with a dissecting needle to move the gas 
bubbles. Commercial bleaching solutions 
such as Clorox and Purex will do, but a more 
concentrated solution is preferable. Such a 
solution destroys the protoplasm and leaves 
the spicules obscured only by the myriad 
bubbles. These latter may be moved about 
so that the isolated spicules are revealed. For 
permanent mounts one may boil out a sample 
(on a slide) with about six drops of fuming 
nitric acid, later adding balsam and cover 
slip. 
A few words about spicule nomenclature 
may be in order. Megascleres typically make 
up the framework of the sponges in which 
they occur and are always comparatively 
large, sometimes even visible to the unaided 
eye. Microscleres never make up the frame- 
work of a sponge and are almost always 
minute. Some have a distinctive shape, and 
when such a shape is found to be large, that 
spicule is still regarded as being a microsclere 
in spite of its size. Megascleres may have 
three or more rays diverging from a central 
point (triaxon, tetraxon, etc.) or, instead, 
may be monaxon. The latter may be sharp 
at both ends (oxeas) or at only one end 
(style). If rounded at both ends they are 
called strongyles; if swollen at both ends 
they are called tylotes. A tylostyle is swollen 
at one end, pointed at the other. The prefix 
"acantho” means spiny. Microscleres may be 
very thin rods (raphides), S- or C-shaped 
(sigmas), or archer’s-bow-shaped (toxas). 
Some are asters, covered with long rays. 
These are termed euasters if all radiate from 
a point, but are called streptasters if the rays 
radiate from a rod or bar. Amphidisks or 
birotulates have a circular pattern at each 
end of a rod. Related forms called chelas 
are so elaborate that they require illustration; 
some resemble anchors. If both ends are 
alike, it is an isochela, but if the ends differ 
it is an anisochela. 
KEY TO GENERA 
The commoner species occur in the genera 
marked with an asterisk. 
1. No proper spicules present ... 2 
Proper spicules present ..... 5 
2. Spongin network present .... 3 
Spongin network absent .... 4 
3. Fibers almost always clear .... 
. . . . . . . . Spongia* p. 7 
Fibers full of debris . . Dysidea p. 9 
4. A few fibers present, no network . 
. . . . . . . Pleraplysilla p. 9 
No fibers present, dermal spongin 
present .... Hexadella p. 10 
5. Spicules of silica present .... 6 
Spicules of calcium carbonate present 24 
6. Spicules rare, skeleton chiefly sand . 
Kaneohea p. 23 
Spicules common 7 
7. Astrose spicules present ..... 8 
Astrose spicules absent 9 
8. Sponge spherical, no twice-bent 
oxeas Tethya* p. 30 
Sponge not spherical, twice-bent 
oxeas present . . Zaplethea p. 32 
9. Some spicules triaxon . Plakortis p. 33 
No spicules triaxon . . . . . .10 
10. Ectosomal spicules the same as those 
of endosome . . . . . . .11 
Ectosomal spicules different from 
those of endosome . . . . .20 
11. Larger spicules diactinal . . . .12 
Larger spicules monactinal . . . .15 
12. Diacts are strongyles 
Xytopsiphum p. 11 
Diacts are oxeas 13 
13. A fine-mesh dermal network present 
. . . . . . Callyspongia* p. 12 
No such dermal net present . . . 14 
14. Spicules oxeas and small toxas . . 
. . . .... Toxadocia* p. 16 
Spicules oxeas and raphides . . . 
. . . . . . . Neoadocia p. 15 
