REPORT ON THE TUNICATA. 113 



distinctly nucleated, closely resembling the epithelial lining of the blood-vessels in the 

 peduncle of Culeolus murrayi. No blood-corpuscles were noticed in the interior of this 

 tube, but there can be little doubt that it is a great sinus in connection with the blood- 

 vessels of the mantle. 



The wall of the tube has the same structure as the test over the body, and has no 

 vessels in it. The outer surface is very smooth, and has no foreign matter adhering or 

 imbedded as in the last species. 



The Mantle is a very delicate membrane which does not adhere closely to the test 

 as in Culeolus recumbens, but is easily separated. The musculature is feeble, and 

 consists, as in the last species, of intersecting bands of fibres. The network formed, 

 however, is very irregular, as the bands are not arranged in parallel series. 



Tlie Branchial Sac is more delicate than that of Culeolus recumbens. As in that 

 species there are several longitudinal folds on each side of the sac, but they are very 

 slight, being of the simplest form possible — merely a second internal longitudinal bar 

 attached to each of the normal ones by a short connecting piece at each transverse 

 vessel (PI. XL fig. 11, ir.f.). These secondary internal longitudinal bars, representing 

 the ful i Is, project into the interior of the cavity. The transverse vessels are moderately 

 wide, all of one size, and placed distantly. Occasionally, however, much slighter inter- 

 mediate transverse vessels are present (PI. XL fig. 11, tr.'), dividing the meshes. 



The meshes formed by the intersection of the large transverse vessels and the internal 

 longitudinal bars are nearly square, the antero-posterior extent being generally slightly 

 the greater. Each mesh is divided into two by a delicate longitudinal vessel running from 

 each transverse vessel to the next, and placed about midway between the two internal 

 longitudinal bars (PL XI. fig. 11, l.v.), so that, going round the sac dorso-ventrally, one 

 comes upon two internal longitudinal bars united to form a fold, a narrow longitudinal 

 vessel uniting the transverse vessels, and then other two internal longitudinal bars, and 

 so on. These narrow longitudinal vessels springing from the transverse vessels are of 

 course homologous with the fine interstigmatic vessels of most branchial sacs, so that in 

 the present species the mesh might be correctly described as containing two stigmata. 



In the portions of the branchial sac examined, no calcareous spicula were detected ; 

 but as in some of the other species the spicules were absent over considerable areas, and 

 as they are sometimes very small and difficult to distinguish, I prefer to think that 

 spicules, though doubtless few and minute, are probably present in this species, than to 

 suppose that it differs from all the other species of the genus, which it otherwise so closely 

 resembles, in this important particular. 



T/ie Endosti/le. — This organ is narrow, and not nearly so conspicuous as in Culeolus 

 recumbens. The most striking peculiarity, however, is that no calcareous spicules can be 

 detected in any part of it. 



As in all the preceding species of Culeolus, there is a clear edge on each side, and a 



