OSCULA AND ANATOMY OF LEUCOSOLENIA CLATHRUS. 493 
brought in by the fishermen was widely expanded, with large 
open oscula. In a few hours it contracted completely, the 
tubes shrinking to perhaps one tenth of their former diameter, 
and having no visible oscula. The following morning, being 
placed in a current of pure sea water, it again expanded to its 
former dimensions and opened its oscula; but the current 
being stopped, it slowly contracted again. In the evening I 
again placed it in the circulation, and the next morning it was 
expanded a third time, though not in all parts, the tubes 
furthest removed from the oscula being to a certain degree con- 
tracted. Some of its oscula opened completely, others were 
closed and breast-shaped, but at least visible ; whereas, in its 
completely contracted state, it was impossible to see that the 
sponge had ever had oscula. On the strength of these so oft- 
repeated observations, I cannot but state my disbelief that any 
Ascon (or any sponge) is permanently lipostomous; and 1 
have no doubt that where von Lendenfeld has described Aulo- 
plegma forms, e.g. in Ascetta spinosa (op. cit., p. 203), 
he has simply overlooked the oscula, as he has certainly done 
in Ascetta clathrus. The large granular cells in Forms B 
and C admit of a very simple explanation; they are simply 
closed pores, which the author has overlooked in Form D, where 
they are equally common. Other points of histology I hope 
to criticise in another place. I will only draw attention to 
the statement (p. 190), that in sponges the ‘‘ skeleton form- 
ing, sexual, and muscular cells are formed in the mesoderm, 
and are not of epithelial origin ” (compare also the account of 
the “zwischenschicht,” pp. 398—405). After what I have 
already written, this statement requires no further comment. 
Napies ; lst March, 1892. 
