CHAP. 1X. ] THE DEEP-SEA FAUNA. AT 
or slightly-cupped disk, with a papilla in the centre 
receiving the upper end of the coil, with large oscular 
openings, and a fringe of delicate radiating spicules 
round the edge, was the top of the sponge, spreading 
out probably level with the surface of the ooze. 
In essential structure Hyalonema very closely re- 
sembles Holtenia, and the more characteristic forms 
of the Hexactinellide. The surface of the sponge is 
supported by a square network, formed by the sym- 
metrical arrangement of the four secondary rays of 
five-rayed spicules, and the sarcode which binds these 
branches together is full of minute feathered five- 
rayed spicules, which project from the branches like 
a delicate fringe. The oscula are chiefly on the upper 
disk, and lead into a number of irregular passages 
which traverse the body of the sponge in all direc- 
tions. When we trace its development, the coil 
loses its mystery. On one of the Holtenie from the 
Butt of the Lews, there was a little accumulation 
of greenish granular matter among the fibres. On 
placing this under the miscroscope it turned out to 
be a number of very young sponges, scarcely out of 
their germ state. They were all at first sight very 
much alike, minute pear-shaped bodies, with a long 
delicate pencil of silky spicules taking the place of 
the pear-stalk. On closer examination, however, these 
little germs proved to belong to different species, 
each showing unmistakeably the characteristic forms 
of its special spicules. Most of them were the young 
of Tisiphonia, but among them were several [Holtenia, 
and one or two were at once referred to Hyalonema. 
In two or three hauls in the same locality we got 
them in every subsequent stage—beautiful little 
