REPORT ON THE HYDROIDA, ie 
branches. It is polysiphonic or fascicled, when it is composed of several mutually 
adherent tubes; monosiphonic when consisting of a single tube. In some species the 
cavity of its perisarc is constricted at intervals by annular ridges or imperfect septa— 
intracauline ridges. 
Hyprociapia.—The hydrotheca-bearing ramuli—almost always the ultimate ramuli 
—of the hydrocaulus in the Plumularidee. 
Racuis.—That portion of the hydrocladium which supports the hydrothece. That 
portion of the phylactocarp which supports the costz or their equivalents. 
InternopE.—The part of the hydrocaulus which intervenes between any two 
consecutive joints. 
Cawosarc.—The common organised fleshy portion of the hydrophyton; the living 
bond by which the zooids are organically united to one another. 
NematopHores.—Peculiar bodies developed in certain genera from definite points of 
the hydrosoma, and consisting of a chitinous receptacle with protoplasmic contents, in 
which thread-cells are usually immersed. They are eminently characteristic of the 
Plumularide. 
GonopHoreE.—The ultimate generative zooid which gives origin directly to the 
generative elements—ova or spermatozoa. 
Gonanctum.—An external chitinous receptacle within which in the calyptoblastic 
genera the gonophores are developed. 
BuiastostyLe.—An extension of the ccenosarec through the axis of the gonangium in 
the form of a fleshy column frum whose sides the gonophores are developed as buds. 
Acrocyst.—An external sac which in certain hydroids is formed on the summit of the 
gonangium, where it constitutes a receptacle into which the ova are discharged in order 
to pass within it through some of the earlier stages of their development. 
Puyacrocarr.—A part of the gonosome specially modified for the protection of the 
gonangia in certain genera (phylactocarpal) of the Plumularidee. 
CorsuLta.—A form of phylactocarp constituting a basket-shaped receptacle which 
encloses groups of gonangia in certain phylactocarpal Plumularidee. 
Cost#,—Rib-like appendages which form part of the protective arrangement in 
certain phylactocarps. 
Gymnosiastic.—The condition of a hydroid when no external receptacle (hydrotheca 
or gonangium) invests either nutritive or generative buds. 
CatyprosLastic.—The condition of a hydroid when an external protective receptacle 
(hydrotheca or gonangium) invests either the nutritive or generative buds, 
(ZOOL. CHALL. EXP.—PART Xx.—1883.) U3 
