APPEXDIX A. 491 



that the case harlly aflmits of bcin^ fully stated without a certain amount of pro- 

 lixity, which I would gladly avoid ; and there is, moreover, the difficulty that some 

 points in the history of these creatures, almost essential to a satisfactory verdict, have 

 not been setthnl hy observation, or more than barely touched by negative evidence 

 of very limited scope. The points, therefore, I shall now draw attention to, are sub- 

 mitted, not with the expectation of their lar<;ely conducinf;; to a positive conclusion, 

 but to show that there exist certain diflicultics in the way of the unreserved 

 acceptance of the generally received notion tluit the parasitism of the Siphmictdun and 

 tlic Ifeteropiammia is in kind identical with that of any extraneous lodger, who taUes 

 up his abode in the body of another animal, as the J'ldex penetrans does beneath the 

 human integument, or the female Sti/lops within the body of the bee. 



J/eteropKiiiiiMia Mir/ie/iiii is a perfectly free coral of rather less usually than three- 

 quarters of an inch in its longest diameter and pyritbrni in the horizontal section of 

 its base. The basal surface is smooth, and at the narrow end is perforated by a 

 circular hole, which is the external opening of a curved tube lodged within the base 

 of the coral and forming a regular curved gallery therein, occupied by the Siphuncuhix. 

 Above, the coral is crowned by an ordinary calyx, either narrowed or constricted in 

 the middle, or divided into two separate calices, which are ranged unsymmetrically 

 and without reference to the elongate axis of the horizontally pyiiform base. The 

 relations and character of this gallery or tube demand careful consideration, and the 

 following points regarding it, both negative and positive, may be dwelt on, as helping 

 to solve the question of its origin and precise connexion with the coral wherein it is 

 lodged. 



Firstly, it would seem to be a concomitant structural character necessarily 

 present in neteropnammia, and included th(;n;fore among the characters of that genus. 

 This would not be the case were any instance known of specimens of this genus un- 

 provided with the gallery in question. The gallery is not formed by a shelly tube, 

 such as invests the burrow of a Teredo, or is secreted by a Spirorhis or Vermetun. 

 The wall of the gallery is composed of the naked coral skeleton, and its existence is 

 due simply to the arrested growth of that structure, as round some foreign body. 

 Kow in considering this gallery or tube, under the conditions above described, we have 

 three separate reasons for doubting the ordinary and accepted view of its relation to 

 the structure which incloses it. There is the fact that without this gallery there is 

 no Ueteropsummia, and on the supposition that the gallery is simply bored by the 

 Siphunculus, as a Teredo might bore into a log of wood, we have the remarkable fact 

 to dispose of, that no ILteropsammia is ever discovered which has escaped attack, and 

 the no less remarkable fact that no Heferopsammia is ever seen attacked by more than 

 one Siphunculaa, and also that the Siphunculus m question confines his ravages to a 

 few species of the genus HeteropMmmia, which is strange, if we suppose the Siphun- 

 culm to be possessed of the power and will of boring into the structure of living coral. 



Secondly, a number of aquiferous pores or tubes, forming a ring below the calyces 

 on the upper surface, communicate with the internal galleiy, and bear, I think, strong 

 evidence to its structural relationship to the coral wherein it is situated. For, granting 

 that the Siphunculus is possessed of the power of excavating for itself the cavity where 

 it is found lodged, yet the same organs which would serve to excavate the larger tube 

 could hardly be so adajitcd as to perform the task of making the minute perforations, 

 at right angles to the main tube, which I have termed aquiferous pores, whoso func- 

 tion is clearly to admit the ambient sea to the internal gallery, or at least to bring it 

 within access of its wall. Doubtless these aquiferous pores arc advantageous to the 

 Siphunculus occupying the gallery, but that they were formed by that creature is by 

 no means ociually clear. 



Thirdly, the pyi-iform shape of the coral, with its evident co-relation to the growth 

 of the Siphunculus, completely disposes of the idea that the adult coral is attacked and 

 perforated by the Siphunculus, as in that case there is no reasonable explanation why 

 the orifice should be lodged in the advanced portion of the coral, and in that case the 

 Siphunculus having effected its entry into the viscera (speaking metaphorically) of the 

 coral, would be compelled to turn roinid on itself within the narrow compass or 

 gallery wliicli it so completely fills. For the position of the Siphunculus is that of its 



