ON APPENDICULARIA FLABELLUM 45 S 



by tubular prolongations of the branchial clefts into the body, so as 

 either to become directly mixed with the blood, or by some further 

 ramifications of the tubes to act through their thin walls on the sur- 

 rounding blood. Which of these possibilities really occurs must 

 remain, for the present, undecided ; for although in A. cophocerca the 

 end of the respiratory tube may be seen very clearly, yet it is still 

 uncertain whether a bent prolongation of it may not be continued 

 from this point, and may not, by presenting a transverse sectional 

 view, give rise to the appearance of an end. I will enter no further 

 in this place into the discussion of possibilities, my principal object 

 being the statement of facts. However, I believe I have demon- 

 strated that there is a tolerably-marked difference between the 

 respiratory system of the Ascidians and that of the AppendiciilaricB, 

 expressed morphologically by the tube proceeding from the respiratory 

 apertures of the latter.'' 



Excessively puzzled to understand how structures so well marked 

 and so obvious as these should have escaped my notice, I was, as may 

 be imagined, very desirous to re-examine Appendicularia ; but 

 although its occurrence in the British Isles was already recorded,""- I 

 hardly hoped to find it at accessible distances from the shore. During 

 a few calm days last autumn, however, the water of the Bristol Channel, 

 near Tenby, in Caermarthenshire, swarmed with Appendiadm icB (in 

 company with annelide and crustacean larvae, Sagitta, echinoderm 

 larvffi, MeduscE, and Noctihicce), very little different from the southern 

 species which I had previously described, and I gladly seized the 

 opportunity of repeating my observations. 



The length of the body of different specimens varied very much ; 

 from one-fifth of an inch to a fifth or sixth that size. The caudal 

 appendage was three or four times as long as the body, broad, 

 flattened, and rounded at its extremity. The whole animal was 

 usually colourless, except that the stomach had a brownish hue. In 

 one instance, however, the caudal appendage was stained of a bright 

 crimson colour, from what cause I know not. 



With regard to the internal anatomy of the animal, I have, in the 

 main, to confirm the statements I originally made. The oral aperture 

 appeared to be more distinctly bilabiate than I had observed it to be 

 in the southern species, the upper lip hanging over the aperture, and 

 being, as it were, enclosed by the concave edge of the lower. The 

 test forms a thick coat upon all parts of the body, except the posterior 

 region, over the testis, where it is excessively thin. It often separates 



1 On the coast of Scotland. See Forbes and Hanley, " British Mollusca," vol. iv. 

 p. 247. 



