OF THE SOFT PARTS IN EUPLECTELLA ASPERGILLUM. 665 
there externally, while the side and inner surfaces of the siliceous beams, which 
are here particularly strong and thick, are only covered by a thin membrane. 
At the lower extremity of the sponge the soft parts end with the netting of 
the tube-wall. The terminal tuft of long siliceous hairs, which serve to anchor 
the sponge in the ooze, show no appreciable soft parts. 
As in other sponges, we can only obtain a clear idea of the structure of the 
soft parts, and of their relation to the skeleton in Huplectella, by the prepara- 
tion and careful study of thin sections. 
Tinging with different dye-matters is of essential service for defining the 
differentiation of tissues and their peculiar cell-elements. 
To make preparations which answer both purposes I proceeded as 
follows :— 
Pieces from the size of a pea to that of a bean were cut with fine scissors 
from the fragments which had been preserved in absolute alcohol, and freed 
from the excess of alcohol by being laid on blotting paper for a little. They 
were then tinged, some with picro-carmine, some with aloin-carmine, and . 
others with hematoxylin, for which, as a rule, from six to twenty-four hours 
was necessary. After the pieces so dyed had been well washed in distilled 
water, they were laid in alcohol of 52°, then in alcohol of 60°, and by gradual 
concentration were finally brought to absolute alcohol. Out of this they were 
put next day in a mixture of absolute alcohol and xylol, and finally in oil of 
turpentine. Completely drained in this way, they were embedded in paraffin, 
and divided by Leyser’s microtome in different directions into fine sections, 
which, after the paraffin has been removed by warm oil of turpentine, were 
preserved in Canada balsam. 
A good general view of the arrangement of the soft parts is most easily got 
by a fine section of the tube-wall, taken transversely through a comb at a point 
where the inner surface of the wall shows a quadrate area with a large canal 
opening. I have figured such a section (Pl. X VII. fig. 3) ina combination figure, 
2.é., in a drawing as like nature as possible, made up from several preparations, 
fifteen times the natural size. We observe, in the first place, that the whole 
external surface is covered by a delicate membrane, which extends between 
the outer points of the radiating rapier-like six-rayed spines and the floricome- 
hexradiate spicules of BowErBANK * which always lie close to the rapier hilt, in 
such a fashion that it always appears more or less depressed in the middle 
between each group of the four rapier hilts and floricomes which mark the four 
corners of a quadrate area. This membrane, which may be simply called the skin, 
when seen from above (Pl. X VII. fig. 5), is pierced like a sieve with numerous 
round or oval holes of different sizes. These dermal pores are only wanting 
* For shortness I will call the dainty six-rayed stars, composed of six eight-membered structures 
like the cup of a flower, “ floricomes.” 
