On the organic tissues in the bony structure of the corallidæ ... read Apr. 21, 1842 / [James Scott Bowerbank].

  • James Scott Bowerbank
Date:
[1842]
Catalogue details

Licence: Public Domain Mark

Credit: On the organic tissues in the bony structure of the corallidæ ... read Apr. 21, 1842 / [James Scott Bowerbank]. Source: Wellcome Collection.

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    of these large cylindrical vessels may be traced for a considerable distance, and many similar junctions of the large and small tissues be observed. They do not always join the larger so precisely opposite to each other as in the instance figured ; but in all the cases observed, the valves in each of the tissues were present, although not always in the same relative position in the large vessel, being sometimes on the contrary side of the mouths of the smaller ones to that represented in the figure. Occasionally, but very rarely, a valve is to be seen in the larger vessels where no junction with the smaller ones takes place. I have been unable to trace the large vessels to their natural terminations, but it is probable that they originate at the bases of the polyp cells, and that the valves with which they are furnished, were designed by nature to prevent the retrocession of the chyle, elaborated in the digestive organs of the polyps ; and this idea is strengthened by circumstances which I shall hereafter describe. The difference in the structure and characters of the larger and the smaller of these vascular tissues would seem to indicate that they have separate and distinct func- tions ; in the former we observe them maintaining a uniform diameter throughout a long course without once branching or dividing, while the latter immediately de- creases in size, dividing and subdividing until they terminate in vessels of extreme minuteness. The valvular structure is also a character peculiarly distinctive of the larger system ; as there is not the slightest indication of such organs in the smaller vessels throughout the whole of their course, subsequent to their junction with the larger tissue. Several other corals that I examined exhibited this valvular tissue with very little variation in its character from that of Millepora alcicornis, but in one specimen (Cellepora pumicosa) it differs in so great a degree as to render a description of it necessary. Instead of being of an uniform character, and pursuing an unbroken course for a considerable length, as in Millepora alcicornis, it varied continually in its size, contracting in some parts to half or a third of the diameter that it exhibited at others, and especially so at the parts where the valves are situated, as represented at a, b, and c, fig. 3. Sometimes, as at the point a, fig. 4, it is terminated by an abrupt runcation and a slight lateral expansion. At each of these parts there is a valve and a new branch produced. In some cases, as at d, fig. 3, there is but a single branch given off with the usual valves in the branch and main trunk ; and in others, as at b, fig. 4, there is the same form of structure observed which is so characteristic of this description of vessel in Millepora alcicornis. The branches given off in all the cases figured from the Cellepora were not belonging to the fine complex system of vessels, but of the same nature as the parent ones, giving off secondary branches, as represented at c, fig. 4, which have the valvular structure in every respect like the main vessel. I could not trace the connection between this valvular system of vessels and the minute contorted system with ceecoid projections, although the latter was present in abundance ; but it may be fairly presumed from the result of the examina- tion of the Millepora, that such a junction does take place. About the same propor- MDCCCXLII. 2 F
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