372 DR. ALLMAN ON THE ANATOMY AND PHYSIOLOGY OF CORDYLOPHORA. 
is here much contracted, the endoderm resembles in all respects that of the stomach, 
except in the absence of distinct rugse ; but as the ccenosarc passes backwards under 
cover of the polypary, the cells lose their elongated form, the endoderm becomes 
thinner and the canal proportionately wider. Throughout all the rest of the ccenosarc 
the endoderm is formed of a compact tissue destitute of rugae, but whose component 
cells continue to retain their glandular character (fig. 10). 
The canal of the ccenosarc is filled with a fluid containing globular and irregular 
corpuscles of various sizes ; these corpuscles may be observed to exhibit a kind of 
circulatory movement, which however is very irregular; they maybe sometimes seen 
running from below upwards and again turning round in order to take a retrograde 
course ; the motion of each corpuscle is generally confined to a small circuit, frequent y 
not exceeding the diameter of the canal ; sometimes many of the corpuscles stop 
altogether and allow others to pass them, while sometimes no motion whatever can 
be observed in any of the contents. The corpuscles while moving in their linear 
paths have besides a peculiar vibratile or tremulous motion in themselves, and this 
motion may generally be witnessed while the corpuscles are otherwise entirely at 
rest. The motion of the corpuscles may be traced all through the stems and branches, 
and even into the stomach. The cause of this phenomenon is very obscure ; the 
existence of vibratile cilia on the walls of the canal might be adduced as an explana- 
tion, but these organs have never been made the subject of direct observation, not- 
withstanding the most careful attempts to demonstrate them ; it appears to me that 
the true cause is to be found in currents produced by the active vital processes pmg 
on in the secreting cells of the endoderm, processes which we can hardly imagine to 
take place without causing local changes in the chemical constitution of the fluids m 
immediate contact with the cells, and a consequent disturbance of the stability of 
these fluids. 
3. Muscular System. 
Under this head may be described the only specialized motor apparatus which 
these animals present. It consists of numerous longitudinal fibres, which are in 
close contact with the inner surface of the ectoderm. These fibres (fig. 3 i, i, fig.^4/, 
fig 9 c) may be seen in all the naked portion of the ccenosarc, and in the body of the 
polype, and may be thence easily traced into the tentacula, in which they can be 
followed to the remote extremities of these organs, but they disappear where the 
ccenosarc passes under cover of the polypary. There can be little doubt that we are 
correct in considering them as the representatives of a muscular system, and m 
attributing to them the chief share in effecting the various changes of form which 
the polypes are perpetually presenting. Similar fibres may be witnessed in Coryne, 
Syncoryne, and other marine Tuhidariadae, in some of which they are even more 
distinct than in CordylopJiora. In none could I detect the least trace of transverse 
striee. 
