4 
even those which may be proved to be developed directly from the egg, cannot, 
in a philosophical system, be separated from the others*. 
ON THE REPRODUCTIVE SYSTEM IN THE HYDROIDA. 353 
I. Skercu or THE GENERAL MorpHotocy or tHE Hyprorpa. 
The Hyproma, wherever our knowledge of them is sufficiently complete 
to justify us in arriving at any conclusion regarding the entire life of the in- 
dividual, are all, with, so far as we yet know, only a single exception, composite 
animals at one period of their existence, each consisting then of an assemblage 
or colony of zooidst in organic union with one anoéher. The colony thus 
formed constitutes the “ hydrosoma” of Huxley. 
The associated zooids are always of two kinds (fig. 1). In one (a, 6,¢,d,e) 
Fig. 1.—Campanularia Johnstoni, showing the trophosome and gonosome. 
el Re ot Sr; 
a, b, c, d, e, various parts of the trophosome, and f, g, of the gonosome. 
a, Polypite expanded ; the tentacles are in a single verticil, but when fully extended are 
eld with the alternate one elevated and depressed ; 6, polypite retracted ; c, empty hy- 
heca ; d, stem supporting the polypite and hydrotheca; e, creeping stolon; /f, go- 
ia containing gonophores, which in the present species are in the form of complete 
ophthalmic meduse ; g, one of these meduss just after its escape from the gonan- 
aw 
: _* The recent coral-group Tabulata, and the extinct one Rugosa, are referred by Agassiz 
tothe Hyprorpa. Our knowledge of their structure, however, is as yet very imperfect ; 
and as we know nothing whatever of their generative phenomena, I shall make no further 
| reference to them in the Report. 
Ae the introduction of the very convenient term “ zooid”’ into the language of zoology 
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A 
