44 



scissors, and even then tlie work was anything but clean. In 

 some parts nothing remained but the membrane, together with 

 a portion of the softer tissue on the inner surface, in which, as 

 seen under a simple lens, were numerous small pits, and at the 

 bottom of each of these there was a small opening leading to 

 the exterior (see «, fig. 1). On that part of the membrane 

 where the removal had been less successful there remained 

 numerous minute bodies, which at a glance proved the correct- 

 ness of Professor Tate's diagnosis, each of these being a small 

 Ascidian with its branchial chamber or pharynx, according as 

 we adopt Professor Huxley's or Professor AUman's nomen- 

 clature, so beautifully shown that I doubt if any dissection of a 

 larger Ascidian could enable a student to get a more accurate 

 knowledge of this structure. The numerous sago-looking 

 bodies which can be seen by the unaided eye are each the body 

 of an Ascidian, having a complicated organization ; but the 

 most striking part of the view is the structure intervening 

 between these bodies and the little openings communicating 

 with the outer world — the so-called branchial chamber or 

 pharynx. Many of these will be seen to be torn from their 

 attachments, but some will be found i7i situ, and afford us a 

 perfect knowledge of their arrangement. If we imagine a 

 Chinese lantern to be divided by horizontal ribs, and the parts 

 between these ribs to consist of many longitudinal bars, 

 separated from each other at intervals, so as to give a bird-cage 

 appearance to the whole, we shall have a rough notion of the 

 appearance of these structures. In some instances the mouth 

 (5, fig. 1) is still attached to the border of the opening. Be- 

 hind this is a conical cap (c, fig. 1) denser and less transparent 

 than the other parts, and composed of long flat fusiform cells 

 with central nuclei. This cap, which fits on to the bird-cage 

 structure, is composed of three or four tiers of perpendicular 

 bars divided by the horizontal ribs as already described. 

 Lender a high power w^e can sometimes see here and there 

 the remains of the cilia attached to these bars, by which, as 

 in all the Ascidians, the animal keeps up a constant flow of 

 water through its system. Each of these perpendicular bars 

 appears to be hollow, having on each side a row of oblong 

 cells with central nuclei. In all the specimens examined there 

 was a thickened structure on the outer side of the bird-cage 

 arrangement {d, fig. 1), and running up as high as the cap. 

 It is certainl}^ hollow, but terminates in a blind extremity. It 

 has often been asserted that this structure being hollow serves 

 as a means of conveying fluid along the walls of the bird-cage 

 structure, and that the transverse bars are also hollow, and 

 open into this tube. It is probable that the large tube may have 

 some uses of this sort, but I have here a preparation adapted 



