OSCULA AND ANATOMY OF LEUCOSOLENIA CLATHRUS. 477 
The Oscula and Anatomy of Leucosolenia 
clathrus, O.S. 
By 
E,. A. Minchin, B.A., 
Assistant to the Linacre Professor of Human and Comparative Anatomy, 
Oxford. 
With Plate XXIX. 
As is well known, Leucosolenia clathrus is a sponge 
in which the oscula have been hitherto supposed to be con- 
spicuous by their absence. In Haeckel’s “ Kalkschwamme ” 
will be found a full description of this sponge, together with 
an account of all observations upon it published previously 
to the publication of that monograph. The following is a 
summary of Haeckel’s description ; for further details I refer 
to the monograph itself. 
Leucosolenia (Ascetta) clathrus was first described by 
Oscar Schmidt,! in 18638, as follows :—‘‘ Grantia ramosa, 
ramis 1 mmtro. latis, paulum compressis, varie et irregulariter 
implexis. Oscula in summitate ramusculorum brevium. 
Spicula triradiata, radiis obtusis. Color lete sulphureus.” 
Later? Oscar Schmidt corrected his former description, and 
stated that though he formerly thought he had found oscula 
with a simple lens, he was unable to find them now with a 
“ compositum.” He further stated that he was unable to find 
a trace of a canal system in this sponge; the trabecule 
(Balken) composing it consisted of two very different layers, 
an outer colourless one containing the spicules, and an inner 
1 <Spongien des adriatischen Meeres,’ Suppl. I, p. 24 
? Op. cit., Suppl. II. p. 8. 
