252 EDWARD A. MINCHIN. 
and greater diameter. They arise at intervals from the com: 
paratively minute basal tubes, as if from a creeping stolon. 
Both species are of a pure white colour. The second of the 
two species is, without doubt, Leucosolenia botryoides 
(Ellis and Sol.), Bwk., the Ascaltis botryoides, var. Ellisii, 
of Haeckel. The first, or Ascetta species, I have more diffi- 
culty in identifying. Fig. 14, a, 6, c, represents some of its 
spicules. As may be seen, they are precisely similar to the 
spicule of Leucosolenia coriacea, figured by Bowerbank.1 
On the other hand, they differ somewhat from the figures of 
the spicules of Ascetta coriacea given by Haeckel? in having 
much sharper points, in which they resemble his figures of the 
spicules of A. primordialis.? In his description of the 
spicules of A. coriacea Haeckel states that the spicules are 
“gar nicht, oder nur wenig gegen die Spitze hin verdinnt. 
Die Spitze ist stets stumpf, niemals scharf, meistens glatt 
abgerundet,” &c.4 This description does not apply well to the 
spicules here under consideration ; still less, however, does the 
description ‘“schlank conisch,’’ applied to the spicules of 
Ascetta primordialis, suit them. They have much more 
cylindrical rays than the spicules of A. primordialis. Since, 
moreover, A. primordialis is said to be wanting on the 
Atlantic coasts, and to be replaced there by A. coriacea,? 
this sponge may stand, for the present at any rate, as Leu- 
cosolenia coriacea (Montague), Bwk., the Ascetta cori- 
acea (Tarropsis form?) of Haeckel. It is in Leucosolenia 
coriacea, as here identified, that the sieve membrane occurs 
which I am about to describe. In the summer of 1890 I 
collected a quantity of this sponge in order to make prepara- 
tions for teaching purposes. In vertical sections of the sponge 
passing through an osculum I was at once struck by the 
appearance of a thin perforated membrane stretched across the 
‘Mon. Brit. Spongiadee,’ vol. iii, pl. iii, fig. 14. 
‘Die Kalkschwamme,’ Bd. iii. Taf. v, figs. 2 a—c. 
‘Die Kalkschwimme,’ T. c., Taf. v, figs. 1 a—A. 
Ibid., Bd. ii, p. 30. 
Ibid., Bd. ii, p. 27. 
1 
2 
3 
4 
5 
