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wounded area, until it meets in the centre and the denuded surface of 

 the shell is covered. The new membrane is at first clear and pellucid, 

 but, after a short period, minute vesicular molecules and cytoblasts 

 appear ; solitary spherical cells are next observed dispersed over the 

 surface, especially towards the edge of the wound, and small patches 

 of minute vascular tissue may be seen. As the process of reparation 

 proceeds, the spherical cells increase in size, and assume the form of 

 collapsed vesicles, frequently having a depressed line across their 

 centre, on each side of which there is a partial inflation remaining. 

 As they increase in number towards the edge of the wound, their 

 outlines become more indistinct, until at last they form an even paving 

 or thickening of closely-compressed tessellated cells, whose junction 

 with each other is scarcely to be distinguished. Layer after layer 

 of this tissue follows each other, tier above tier, until the space of the 

 wound is completely filled up. But this portion of the process of 

 reparation, is not effected with anything like the same degree of 

 rapidity that marks the production of the basement membrane, which 

 is frequently perfected, and completely covers the previously exposed 

 surface of the shell, while the restoration of the remainder of the tis- 

 sues has apparently progressed but very slightly, as shown in fig. 8, 

 PI. xvii. which represents a portion of one of the wounded spots, 

 seen with a power of 300 linear. The minute vessels to which I have 

 before alluded quickly make their appearance on the surface of the 

 newly-formed basement membrane, and afford one of the most inte- 

 resting studies of the origin of simple, branched, and anastomosing 

 vascular tisues, that I have hitherto had the good fortune to meet with. 

 In the course of my investigation of the animal tissues of the bony 

 skeletons of the true Corallidae, I have described and figured the vas- 

 cular tissue found in Millepora alcicornis, which is seen to consist 

 of exceedingly minute vessels, simple in their character and frequently 

 terminating abruptly, but having beyond the termination of the truly 

 vascular portion a linear series of cytoblasts, as if the completion of 

 the vessel had been arrested at the period of the death of the animal. 

 In other parts of the same specimen, detached patches of straight 

 and curved linear series of cytoblasts were of frequent occurrence.* 

 In my examination of the animal tissues of Cellepora pumicosa, in 

 the same paper, f I have described a series of large sacculated pro- 

 jections of membranous tissue, supported on the basement membrane 

 of the coral, and crowned, each one, with a large and strikingly 



* Phil. Trans, part 2, 1842, p. 220, pi. 17, fig. 2. f Id. p. 220, pi. 17, figs. 3, 4. 



