STUDIES ON THE COMPARATIVE ANATOMY OF SPONGES. 347 
Notes on the Development. 
My observations on the embryology of Stelospongus are 
as yet necessarily very imperfect, for all the embryos which I 
have yet found are in pretty much the same stage of develop- 
ment. Of this particular stage there is, however, an abundant 
supply, and it presents such very remarkable features that I do 
not hesitate to give a detailed account of it in this place, hoping 
at the same time to be able to extend my observations at a 
later date. 
Historical Account. 
In connection with this portion of our subject it is necessary 
to bear in mind in the first place some very remarkable ob- 
servations of Mr. Carter’s (1, 2, 3, 4, 5), which, though published 
many years ago by such a careful observer, appear to have 
almost entirely sunk into oblivion. The gist of the observations 
referred to is that in the developing gemmule (seed- like 
body. Carter) of Spongilla the flagellated chambers (a m- 
pullaceous sacs, Carter) are formed each from a siugle 
large amoeboid mesodermal cell whose contents break up into 
a number of small cells (germs or ovules, Carter) which 
arrange themselves round a central cavity and develope into 
collared cells. 
A few quotations will suffice to illustrate this point. Mr. 
Carter (4) says that Spongilla “is charged towards the base 
with a number of seed-like bodies of a globular shape, each of 
which consists of a coriaceous membrane enclosing a number of 
delicate, transparent spherical cells, more or less filled with 
ovules and granular matter. ... It has also been shown that 
at an early period of development the spherical, which we shall 
henceforth call ‘ ovibeariug,’ cells are polymorphic — identical 
but for the ovules, with the ordinary sponge- cells — and 
surrounded by a layer of peculiar cells equally polymorphic, 
which I have conjectured to be the chief agents engaged in 
constructing the capsule The seed-like body 
presents a hole, which we shall call the ‘ hi! urn.’ .... 
