CONCHODERMA A.UR1TA. 145 



Size. — The largest specimen which I have seen was, 

 including the peduncle and ears, five inches in length, 

 the capitulum itself being rather above one inch in length, 

 and^ths of an inch in breadth. 



General Remarks. — I have come to the same conclusion 

 with Prof. Macgillivray, concerning the variability of this 

 form, and I believe there is only one true species. With 

 respect to Dr. Coates's species, viz., Otion depressa and 

 0. saccutifera, though I have not seen specimens, I can 

 hardly doubt, from the insufficient characters given, that 

 they are mere varieties. 



With respect to the ear-like appendages, we shall pre- 

 sently see in C. virgata, that at corresponding points on 

 the capitulum (Tab. Ill, fig. 25), there are two slight, 

 closed prominences. According to Professor Macgillivray, 

 in C. aurita, every gradation can be followed by which 

 the appendages, at first closed, become tubular and open. 

 The opening would ensue, if the corium became absorbed 

 at the bottom of the appendages whilst still imperforate, 

 for then the inner tunic would be cast off at the next 

 moult and would not be re-formed, whilst the outer 

 membrane would gradually disintegrate together with the 

 other external parts of the capitulum, and not being 

 re-formed at this point, an aperture would at last be left. 

 These appendages have no relation to the generative 

 system : the ovarian tubes, which surround the sack do 

 not extend into them ; nor do the ovigerous lamellae. I 

 believe, that their function is respiratory : the corium 

 lining them is traversed by river-like circulatory channels, 

 and their much-folded, tubular and open structure must 

 freely expose a large surface to the circumambient water. 

 Why this species should require larger respiratory organs 

 than any other, I know not. In this species, moreover, 

 the filamentary appendages are developed to a greater 

 extent than in any other cirripede ; in most genera, the 

 surface of the body and of the sack suffices for respiration. 



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