On the Gemmules of Freshwater Sponges. 163 
straight specimen seen; and d, shortest capitate specimen seen, 
each about 1-300th inch long. Teeth directed inwards. 
Fig. 5, The same. Capitate spined spicule of the cone and root, about 
1-36th inch long. a, smooth, sharp-pointed, or proximal end ; 
b, spined and capitate or distal end. ‘Teeth recurved. 
Fig. 6. The same. Diagram of four radial-chamber vents, to show the 
sarcodic sphincters in them respectively. a, vent; 6, sarcodic 
sphincter. 
Fig. 7. The same. Diagram of seven cones, to show the position of the 
pores in the triangular spaces between them. a, cone; 8, pore. 
Fig. 8, Sand-grains of the rock on which the variety has grown. 
XIX .—Some Preliminary Remarks on the Gemmules of the 
Freshwater Sponges. By Dr. WitttAM MARSHALL *. 
Tue gemmules of the freshwater sponges, as is well known, 
present in the constitution of their envelopes a series of very 
remarkable peculiarities, which are very different according 
to the species, and which, as adaptations, must have very 
special causes and significations. 
Each germ possesses, according to the species, a round or 
oval, sometimes convexo-concave shell, furnished with one 
opening, or (in Spongilla multiforis, Cart.) with one prin- 
cipal and several subordinate apertures, through which the 
mature contents issue at the proper time. The innermost 
layer of this shell is a firm structureless membrane, which 
Carter t describes as chitinous (‘‘ chiténous coat”), by which, 
no doubt, is meant only that it is “ horny,” without reference 
to its chemical constitution. 
In some few kinds of gemmules this innermost simple thin 
layer is alone present; in others the wall is thicker, and 
appears sometimes very peculiarly modified. Thus in Spon- 
gilla nitens (according to Carter’s { and my own observations) 
and in 8. Cartert (according to Carter) we see that the thick 
capsule is not homogeneous, nor does it show that constitution 
which Carter calls “ granular cell-structure.” Under a low 
power it appears in section to be finely striated radially, and 
its surface, like that of the eye of an insect, appears divided 
up into elegant convex equilateral hexagons ; by the employ- 
ment of higher powers we discover that the lines of striation 
are not the expression of hexagonal corneous pyramids di- 
* Translated by W. S. Dallas, F.L.S., from the ‘ Zoologischer Anzeiger,’ 
1883, pp. 630-634 and 648-652. 
+ Ann. & Mag. Nat. Hist. ser, 5, vol. vii. p. 85. 
t Loe. cit, 
