582 



MAYNARD M. METCALF, 



p. s. H ■ ' i''^^- 



Lin^ 



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Fig. K. A sagittal section through the body of a young Molgula manhattensis. The 

 upper part of the hody was slightly distorted so that the siphons do not show in this 

 section. c.J ciliated funnel, cl cloaca, e.in larger ectodermal invagination, e.in' smaller 

 ectodermal invagination, gg ganglion, gl neural gland, ph pharynx, p.s. n posterior siphonal 

 nerve, r.n rapheal nerve, st stomach, t outer contour of test. 



cloaca. On each side the invagination is not so great, and here the 

 folds serve to support the oviducts, (as shown in Fig. QQ, Plate 38). 

 In all of these invaginations there is found some of the test between 

 the two layers of infolded ectoderm. This is somewhat more dense 

 and tough than the ordinary test of the outer surface and doubtless 

 gives a certain degree of firmness to the folds. 



In this species of Molgula, in addition to the ectodermal in- 

 vaginations just described, there are certain tubular evaginations of 

 the ectoderm, which are of slightly greater interest. These are found 

 mostly over the upper surface of the body, near the siphons and 

 the ganglion. The ordinary ectodermal epithelium is composed of 

 flattened cells, but the epithelium of the tubular evaginations is 

 columnar. In certain places we find patches of similar thickened 

 epithelium which have not been evaginated into tubes. 



