42 ALLMAN, ON POLYZOA. 
a much more highly differentiated structure, in which the organs of diges- 
tion especially hold a dominant position, and which we may regard as sexual 
or non-sexual, according to the view we take of the relation between it and 
the testis. 
“ Now, if the formation of the ovary be attended to, it will be seen that 
this body is developed at a late period from the walls of the original sac- 
like embryo, which have undergone slight changes, and have become the 
endocyst of the more mature Polyzoon; and it will be at once perceived 
that this development of the ovary takes place in a way which may obviously 
be compared with the formation of a bud ; that, at least in Alcyonella, it 
occupies exactly the position in certain cells that the buds destined to 
become polypides do in others, and that at an early stage of polypide and 
ovary it is scarcely possible to distinguish one from the other; so that the 
idea is immediately suggested, that the body here called ovary is itself a 
distinct zooid, in which the whole organization becomes so completely sub- 
ordinate to the reproductive function as to be entirely masked, and appa- 
rently replaced by the generative organs. This would then constitute a 
third zooid, which would therefore be a sexual zooid; it is, however, 
unsexual (female). 
“Tn the next place, we find that upon the funiculus (in Aleyonella), which 
probably belongs rather to the polypide than to the endocyst, there is 
developed the mass described as a testis. Now, if we view this mass as a 
mere organ of the polypide, we must then regard the latter as the second 
sexual or male zooid; but the testis may perhaps be more correctly con- 
sidered like the ovary, as a distinct sexual bud, having the generative 
system so enormously predominant as to overrule and replace all the rest 
of the organization; this bud, like the ovary-bud, being also unsexual, but 
with a male function. In confirmation of this view, it is to be remembered 
that the funiculus has the power of giving origin to a very remarkable form 
of undoubted bud—the statodlast, which, until ulterior development is 
excited in it, has no nearer resemblance to an ordinary polypide bud than 
the testicular mass has; and to this statoblast—so far, at least, as position 
is concerned—the male bud or testis in Alcyonella would therefore be re- 
ig just as the female bud or ovary is related, to an ordinary polypide- 
ud. 
“Tf the above be the correct view, the complete comprehension of the 
Polyzoon will involve the conception of a ciliated sac-like embryo as a 
starting-point, and a series of buds, of which the last term will consist of a 
pair of sexual buds, the others being non-sexual; from the sexual buds a 
true embryo like the first is again produced, which affords the point of 
departure for another similar cycle.” 
The chapter on the “ Homologies of the Polyzoa” contains 
much matter of considerable interest, and the views, in 
many particulars original, therein advocated, are ably stated, 
whilst the entire subject is very fully and satisfactorily dis- 
cussed. Professor Allman adopts the opinion of those who 
see in the tentacular crown of the Polyzoa the represen- 
tative of the branchial sac of the Ascidians, with the im- 
portant modification, however, that it is the transverse 
and not the longitudinal bars of the branchial sac that are 
represented by the tentacles. But as his reasons for the 
adoption of this opinion, with which we are disposed to 
agree, would require to be given at considerable length to be 
