218 
MR. J. S. BOWERBANK ON THE ORGANIC TISSUES IN THE 
tions are observed between the two descriptions of vessels as in the former case, but 
in the Cellepora both the tissues are much more minute than those in Millepora 
alcicornis ; the average diameter of the larger vessel is 5 q 0 q of an inch. Upon 
submitting some fragments of Pavonia Boletiformis to the action of dilute acid, and 
examining the animal matter thus obtained, the same description of membranous 
structure was observed, and a similar fine complex vascular tissue exhibiting irregu- 
larities of the structure, and in other respects so closely resembling that observed in 
Millepora alcicornis as to render a further description of it unnecessary. The larger 
kind of vessels were also present in about the same proportion as in Millepora, but 
they differed from them in some respects, inasmuch as towards their outer extre- 
mities they resolved themselves into a much greater number of branches, all origin- 
ating at nearly the same point, as represented at a, fig. 5, and frequently clustered 
together in such a manner as closely to resemble the distorted tentacula of a dead 
polyp ; but I do not believe that they are in reality the remains of those organs, but 
rather of the great ducts that have terminated at the bases of the polyps ; as we find 
in many instances branches given off from their sides, which are surmounted by 
elliptical ovoid bodies, as represented in fig. 6, which have much the appearance of 
being incipient polyps, or gemmules which had not been projected beyond the outer 
surface of the coral. These bodies are divided at right angles to their axes by two 
or three diaphragms, and present in other respects a cellulated appearance. They 
occur in considerable numbers dispersed amid the tissues, and vary in size from 
aoo ' o to -5-^0 °f an inch in length. The branches are all of them divided at short 
intervals by diaphragms, so as to assume a cellulated appearance, the diaphragms 
becoming more distant from each other as they recede from the apex of the branch ; 
and they are continued to some distance below the point where the branches are 
given off from the parent vessels, until at last they cease to appear, and the tissue 
assumes its usual vascular character. The average diameter of these vessels is 5 - £00 
of an inch. 
Beside the elliptical bodies, there are frequently to be seen large spherical or 
oval brown masses (fig. 7 ), whose diameter averages °f an inch. They are 
nearly opake, but when a bright stream of light is transmitted through their sub- 
stance, they are seen to be filled with irregular cellular structure, or closely com- 
pressed granular matter. They appear always to be attached to, or to be partially 
imbedded in, the membrane, and are connected with each other by a beautiful 
moniliform tissue. When these vessels terminate at the masses, they do not abruptly 
enter its substance, but, dividing into minute ramifications, are spread over and lost 
upon its surface, as at a, fig. 7- In other cases they do not divide in this manner, 
but, preserving their integrity, they attach themselves to the surface, and, passing over 
a third or half of its diameter, detach themselves and resume their course, as repre- 
sented at b, fig. 7- It is difficult to conceive the nature and purposes of these curious 
masses, but they bear a striking analogy to “ the brown bodies ” described by my 
