840 General Notes. 
the three sub-classes Myxospongie, Hexactinellide, and Demo- 
spongiz. The Demospongis he sub-divides into Tetractinellida and 
Monaxonida, the former comprising such Demospongie as have 
some or all of the scleres in the form of tetraxons, trisenes, or 
esmas. 
CasLENTERATA.—The third of the reports composing Vol. 
XXIII. of the Challenger series is by Professor G. J. Allman, and 
forms the second part of his memoir of the Hydroida. Only three 
genera of Gymnoblastic hydroids: Stylactis, Eudendrium, and 
Monocaulos are represented in the Challenger collections. M. impe- 
rator is a most remarkable hydroid, having a stem seven feet long 
though but half an inch thick, and a stretch from tip to tip of 
tentacles of nine inches, so that all other hydroids sink into insig- 
nificance as regards size when compared with it. It was obtained 
at the depth of four miles beneath the surface. The Calyptoblastea 
were well represented in the collection. Idia, Lamoureux, prov 
on thorough examination to be constructed on a quite unique type, 
a new genus, Perisiphonia, represented by two species, was 
discovered. In this genus the axial tube which bears the hydro- 
thecæ is surrounded by numerous tubes set with tubular sarcothece, 
and the hydrothecz projects through interstices in these axial tubes. 
The curious genus Synthecium is enriched with two new species, 
hecocladium with one. 
so traced, may be presumed to have been budded off from fixe 
trophosomes, to compose a separate group, but leaves them to 8n 
planoblasts, and the planoblasts are almost always Anthomedn&ls 
i.e. have the generative elements developed in the walls of 
w 
(6) Rhabdophora or Graptolites. 
Verwes.—Vol. XXIII. of the Challenger series has a sbort 
report upon the Entozoa of the collection, by Dr. O. von Lin 
