10 Mr. W. Saville Kent on Prof: LE. Haeckel’s 
indeed, that has considerably exercised the mind of every 
authority who has devoted his energies to the solution of the 
“ sponge-question,”’ is associated with the so-called ciliated 
germs or larve of certain sponge-forms. This “ ciliated 
larva,” which may in fact be regarded as the veritable “ pons 
astnorum””’ of the whole sponge-problem, has been seized upon 
and trotted round the lists by Prof. Haeckel and all the sup- 
porters of the Diploblastic or Ccelenteric theory of sponges as 
the perfect embodiment of the typical sac-shaped bilaminate 
Gastrea, or the hypothetical stock-form of all animal life from 
the Coelenterata upwards, and as conclusively proving in its 
own personality the necessity of regarding sponges as members 
of the Ccelenterate subkingdom. Put crucially to the test, 
however, it will be found that these ciliated sponge-germs are 
altogether innocent of the blushing honours that have been so 
forcibly thrust upon them. 
As already shown by Metschnikoff*, these somewhat re- 
markable bodies by no means conform, in either external 
characteristics or in the fashion of their development, to 
that arbitrary formula which has been insisted upon by 
Prof. Haeckel, and which was necessary for the vindication 
of his position. It may be further demonstrated now, how- 
ever, that there is no structural or functional aspect asso- 
ciated with these bodies that does not find its parallel among 
the more simple and typical Protozoa, or that cannot be readily 
explained by reference to the phenomena manifested by the 
various members of that group. ‘The only clue to a thorough 
comprehension of the nature of these ciliated bodies is, as 
might be expected, afforded by the study of their development. 
This has been followed out by me in association with Grantia 
compressa, Sycon ciliatum, and other sponges prominent for 
their plentiful production of these disputed structures, the 
evidence adduced in all cases, as detailed and illustrated else- 
where, overwhelmingly indicating that they cannot be regarded 
otherwise than as the results of a specially modified process of 
multiple fission, and that their correct title would be “ com- 
pound gemmules.” Among the ordinary Holostomatous Pro- 
tozoa such a mode of multiple fission following the coalescence 
or fusion of two or more individuals is of frequent occurrence, 
the only point of departure between the two cases being that, 
whereas in the sponges the individual resultants of such mul- 
tiple fission remain in intimate connexion with one another, 
in the more simple and independent forms, as remarked of 
their germs, they become separated and dispersed through the 
* ‘Zeitschrift fiir wissenschaftliche Zoologie, Bd. xxiv. 1874; and 
Ann. & Mag. Nat. Hist., July 1875. 
