DR. A. FARRE ON THE STRUCTURE OF THE CILIOBRACHIATE POLYPI. 415 
together with the circumstance that the particles so brought within its reach seem 
frequently rather a source of annoyance than of advantage to the animal, are points 
which would encourage the belief that these parts have a considerable share in the 
process of respiration ; but until the existence of a circulatory system and its course 
shall have been determined, the consideration of this as a respiratory apparatus must 
yet remain conjectural, though supported by very strong analogies. On the other 
hand, its use in ensuring a supply of food to the animal cannot be questioned. 
The structure and growth of the cells, and their connecting medium, offer many 
interesting points for consideration. In the ramified and creeping species the cells 
are connected by a cylindrical stem, which appears nearly homogeneous throughout, 
and does not present that obvious distinction between hard and soft parts that is ob- 
served in the stems of Sertularia. If, however, this stem be cut across, especially when 
decomposition has commenced, a granular matter flows out, leaving the delicate 
corneous sheath nearly empty. This corneous case of the stem is easily seen to be 
continuous with the cells that arise from it, but the internal substance cannot be di- 
stinctly traced to the animals as in Sertularia. It is probable, however, that it passes 
gradually into the parietes of the body by which the cells are lined. With the facts 
before us of the progressive growth of the stem, and the production from it of buds or 
gemmae, which gradually develop into mature animals, no doubt can be entertained 
either as to the vitality of this part, or of the direct communication between it and 
the young animals, at least up to the period at which they begin to emerge from 
their cells and to seek nourishment for themselves. Nor is it reasonable to suppose 
that this communication ever after ceases, for then it would be impossible to account 
for the nutrition of the growing parts, and the combined operations by which the 
regularity of growth of the whole is maintained, as exemplified in the ramified species 
by the proportionate thickening of the stem to the number of branches which it has 
to bear, and in the definite forms which each species assumes. 
But it might be questioned whether the whole of the stock is a living part, or only 
the soft interior; while the more dense exterior, together with the cell, might be re- 
garded as a mere exudation from it. From the various phsenomena, however, that 
occur during the growth of these parts, and from the manner in which they are 
blended in their early state, I am disposed to consider both the one and the other 
as organized and influenced by one common vitality. 
The two processes of reproduction here observed offer many points of contrast. 
That by gemmae, or buds from the common stock, appears to be uninfluenced by season ; 
the young animals, from the earliest period in which form can be traced in them, 
resemble in some measure the parent ; and their subsequent growth is but a deve- 
lopment of that form, and at no period are they separated from the parts that pro- 
duce them. The process by locomotive ciliated gemrnules is limited to certain sea- 
sons, generally spring ; these bear no resemblance to the parent ; they appear to be 
the more immediate produce of the individuals, than of the community ; and they 
