808 
DE. J. S. BOWBEBANK ON THE ANATOMY 
account of the cilia and their cells in situ. He describes them as forming a single layer 
of spherical cells, 3 -^^ millim. in diameter, and which, though touching each other, are 
not in such contact as to lose their rounded figure. Liebeekuhjt’s description of the 
mode of disposition of these cells in Spongilla would serve equally well for those in 
Grantia compressa. Professor Huxley, in a paper “ On the Anatomy of the Genus 
Tetlnja^' published in the ‘Annals and Mag. Nat. Hist.’ vol. vii. p. 370, describes cells 
and cilia from an Australian sponge, which he designates spermatozoa, and which he 
describes as having “ long, pointed, somewhat triangular heads, about -g^oth of an inch 
in diameter, with truncated bases, from which a very long filiform tail proceeds.” These 
bodies are figured in vol. vii. plate 14. fig. 9. 
On a careful consideration of the descriptions of the ciliated cells seen by the authors 
I have quoted above, it strikes me forcibly that the so-called zoosperms and spermatozoa 
of Caetee and Huxley are identical in origin and purpose vnth the similar organs 
described by Liebeekuhn and those found in situ and in action in Grantia compressa^ 
and, in truth, that they are the homologues of the breathing and feeding organs of 
the zoophytes and more highly organized animals. 
Beproduction. 
The ovaria in sponges exhibit considerable variety in shape and structure. The most 
familiar form is that of Spongilla Jlumatilis, represented in Plate XXXIII. fig. 5, in its 
natural condition. 
These bodies have hitherto been usually designated as gemmules, but this term 
appears to be inappropriate. Each of them contains numerous minute vesicular, 
round or oval molecules, which are discharged from the foramen in succession, and each 
of these appears to be capable of producing a sponge. The terms ovarium and ova are 
therefore more in accordance with the rules of modern nomenclature, and this altera- 
tion in their designation is the more necessary, as I shall hereafter be enabled to show 
that, at least in Tethea lyncurium, propagation by true external gemmation really 
exists. I propose, therefore, for the future that all such large vesicular organs con- 
taining numerous molecules or ova capable of reproducing the species, and of being 
successively ejected from the sponge, should be designated ovaria and ova, and that the 
term gemmule should be restricted to the isolated bodies which pullulate from the 
internal or external surfaces of the parent, and by ultimate separation become each a 
distinct individual. 
The reproductive powers of the Spongiadse have been treated of to a considerable 
extent by preceding authors, and the amount of our information on this subject is, I 
believe, both extensive and accurate. I will not attempt a recapitulation of all that has 
been written on their reproduction, but content myself with a slight sketch of our know- 
ledge of the various modes of propagation that have been well ascertained and described. 
From the researches of the various authors who have written on the structure and deve- 
lopment of Spongilla and on the marine Spongiadse, it appears that there are three well- 
