OF THE SOFT PARTS IN EUPLECTELLA ASPERGILLUM. 671 
the cells of the connective substance, as they are tolerably equally distributed 
-in the fundamental basis, and, in conjunction with their scanty protoplasmic 
ares, resemble the cells of connective tissue in other sponges. Besides 
these ordinary corpuscles of the connective tissue, I met with roundish 
balls of strongly refractive spherules, plentiful in some places, scanty in 
others (Pl. XVII. fig. 8), like those described by MArsHatz in the soft parts of 
different Hexactinellide, and especially of Huplectella aspergillum.* I con- 
sider these granular balls, which certainly belong to distinct cells, as accumu- 
lations of reserve nutrition, somewhat comparable in a physiological sense to 
fat or starch. 
The Genital Products.—I found numerous sperm bails of about 50 pw. in 
diameter in the meshes of the connective tissue, between the meshes of the 
ciliated chambers (Pl. XVIL., fig. 6). The fine thread-shaped appendages were 
certainly no longer recognisable on the small sharply-defined, tolerably 
refractive roundish spermatozoa, which were aggregated in clusters in an 
enclosed space; but I have no doubt as to their signification, as they 
coloured deeply with carmine or logwood, like the moving sperm masses of 
the sponges. 
Like most sponges, Huplectella aspergillum is inhabited by different com- 
mensals. While some of these, such as the much talked of crabs of the genera 
Palemon and Aga, live enclosed like prisoners in the large cavity of the sponge, 
and others among the long spicules of the beard, another group are found in the 
soft parts of the tube-wall. From these last I here select for description a 
microscopic hydroid polyp, which appeared so abundantly in the Euplectella 
from Zebu, preserved in absolute alcohol, that one or more hydranths are found 
in almost every microscopic section of the tube-wall. 
It belongs to the group of gymnoblastic hydroids of AttMAN. The simple 
tube-like coenosare of the hydrophyton, which traverses the soft parts of the 
sponge in the form of a long-meshed net, is attached by isolated pointed 
ectoderm processes to the inner surface of a delicate annulated perisarc. tube. 
From this coenosare tube, which is only about 20 uw. wide, more definitely at 
right angles than the branches forming the network of the tube, there spring 
simple club-shaped hydranths, which project without hydrothece freely into the 
inhalent lacune, and therefore towards the exterior, from the zones of ciliated 
chambers. 
Each hydranth has, close beneath the short hemispherical hypostoma, with 
its terminal oral opening, only two opposite annulated comparatively long solid 
tentacles with a terminal knob richly loaded with sting-capsules, and rather 
* Zeitschrift fiir Wissen. Zool., Band xxv. p. 159, and Pl. xiii. fig. 6 Pl. xv. fig. 60. 
