Notes on the morphology of the Tunicata. 581 



of their secretion. The fact that they are not present in other species, 

 so far as known, and that they are present in Cynthia partita over 

 the whole surface of both pharynx and cloaca, would argue that 

 they are not digestive in function. The pharynx, and of course 

 the cloaca, does not seem to have a digestive function in any of the 

 Tunicata. Possibly their presence may be correlated with the very 

 great development of the muscles of the mantle ; these two features 

 being distinctive of this species. If so, should the glands be re- 

 garded as excretory? It seems to me there is as much reason for 

 so regarding them, as there is for assigning the same function to 

 the neural gland. I am, however, unable to appreciate the evidence 

 upon which rests belief in the renal nature of the neural gland. 

 The neural gland and the cloacal and pharyngeal glands must, for 

 the present, be regarded as organs of unknown function. 



Section VII. 



On certain Ectodermal Eyaginations and Inraginations in 

 Molgula manhattensis. 



It [is well known that, among the Tunicata, the ectoderm is 

 often slightly invaginated at points where the muscles are inserted 

 upon its basement membrane. This is probably to give greater 

 firmness to the attachment. In Molgula manhattensis we see many 

 such slight invaginations at the bases of the siphons, where they 

 furnish places of attachment for the retractor muscles of the siphons 

 (Text-Fig. K e. m'). 



There is one such invagination of very great size, which pushes 

 in from the lower posterior part of the body and serves to support 

 the intestine, the gonadial ducts of the two sides, and, on the median 

 line, furnishes a very firm point of insertion for the rapheal muscle. 

 The external aperture of this invagination is in the form of a cres- 

 centic slit, having the position shown in Text-Fig. J. In sagittal 



Fig. J. Molgula manhattensis as seen from behind. The dotted 

 line indicates the position of the aperture of the great ectodermal in- 

 vagination. 



section of the body of the Ascidian (Text-Fig. K) the infolded ecto- 

 derm (e. in) is seen to reach half way to the ganglion, its lower part 

 supporting the viscera, while the upper part projects freely into the 



