MR. T. H. HUXLEY ON THE AFFINITIES OF THE MEDUSAE. 
429 
71 . What has now been advanced will perhaps be deemed evidence sufficient to 
demonstrate, — 1st, that the organs of these various families are traceable back to the 
same point in the way of development ; or 2ndly, when this cannot be done, that 
they are connected by natural gradations with organs which are so traceable, in 
which case, according to the principles advanced in 57, the various organs are 
homologous, and the families have a real affinity to one another and should form one 
group. 
72. Perhaps the view that I have taken will be more clear if I throw it into a 
tabular form, placing opposite one another those organs in the different families, for 
the homologies of which there is, I think, sufficient evidence, thus : — 
Stomachs identical in Structure throughout. 
Medusce. Physophoridce. Diphydcc. Sertularidee. Hydra. 
Disc 
Canals 
Common cavity 
Canals of branches (Rhiz.) 
Natatorial organ Natatorial organ. 
Canals of natatorial organ... Canals of natatorial organ. 
Common tube Sacculus and common tube. Cavity of stem. 
Tentacles, 1 
2 
Generative organs 
Marginal vesicle . . 
Bract 
, A 
...Thickened edge of stomach 
...Prehensile organs 
r Generative sac 
I Natatorial organ of generative sac, 
.Polype-cell. 
■v 
•Oval tentacles. 
.Clavate organs ...Tentacles (.^). 
.Generative organ... Generative organ. 
Natatorial organs (Coryne). 
73 . It appears then that these five families are by no means so distinct as has 
hitherto been supposed, but that they are members of one great group, organized 
upon one simple and uniform plan, and even in their most complex and aberrant 
forms, reducible to the same type. And I may add, finally, that on this theory it is 
by no means difficult to account for the remarkable forms presented by the Medusae 
in their young state. The Medusae are the most perfect, the most individualized 
animals of the series, and it is only in accordance with what very generally obtains in 
the animal kingdom if in their early condition they approximate towards the simplest 
forms of the group to which they belong. 
74 . I have purposely avoided all mention of the Beroidae in the course of the 
present paper, although they have many remarkable resemblances to the animals of 
which it treats ; still such observations as I have been enabled to make upon them 
have led me to the belief, that they do not so much form a part of the present group 
as a link between it and the Anthozoic Polypes. But 1 hope to return to this point 
upon some future occasion. 
Sydney, April 24th, 1848. 
Since the above was written I have had an opportunity (by the kindness of 
W. MacLeay, Esq., to whose advice 1 am much indebted) of reading M. Dujardin’s 
“ Memoires sur le Developpement des Meduses et des Polypes Hydraires,” contained 
3 K 
MDCCCXLIX. 
