112 JOHNS HOPKINS UNIVEESITY MOEPHOLOGICAL MONOGEAPHS. 



dermal tube, d'. The relations of the left half of the pharynx of a left- 

 hand salpa and the left half of its endostyle are, of course, the same; 

 but as the sections which are figured in the plates do not cut the two 

 salpse at the same points, it will be best to trace these structures also. 

 Starting as before with Fig. 10 of Plate XXXIX, we can follow the left 

 half of the pharynx, 28, and the left half of the endostyle of the left- 

 hand salpa through Figs. 1 1, 12, 13, 14, 15, 16, 17, 18 and 19, and we find 

 that like the structures on the right of the right-hand salpa they are 

 uninterrupted, and we also notice that in section 15 the left half of the 

 pharynx becomes separated from a small tube, 28, which can be followed 

 through sections 16, 17, 18, 19, 20 and 21 until in section 23 it opens into 

 the endodermal tube, d'. The relations of these parts are thus seen to be 

 exactly as they are represented in cut W 27. The relations of the left 

 halves of the endostyle and pharynx of a right-hand salpa are more 

 complicated, as are also of course those of the right half of a left-hand 

 salpa. Starting as before with Fig. 10 of Plate XXXIX, we will follow 

 the left half, 28, of the right-hand salpa. Figs. 11, 12 and 13 show little 

 change. In Fig. 14 the left half of the endostyle d 2 becomes stretched out 

 towards the far side of the stolon. In Fig. 15, the left pharyngeal pouch 

 28 has divided into two tubes, one on the right side of the stolon, which 

 comes to an end in Figs. 17 and 18, and one on the left side of the stolon, 

 also marked 28, which can be traced through all the figures, until "in 

 Fig. 23 it opens into the endodermal tube, and then goes on, as shown 

 at 28 in Plate VIII, Fig. 2, over the top of the stolon to expand again, in 

 Fig. 21, into the left half, 28, of the oral end of the pharynx. Tracing 

 the right half, 27, of the pharynx of the left-hand salpa in the same 

 way, we find it, in Figs. 14, 15 and 16, passing with the right half of the 

 endostyle on to the right side of the stolon, and after passing over it, 

 reappearing, at 27 in Fig. 18, at the oral end of the pharynx. 



These connecting tubes are shown in Plate VIII, Fig. 2, for the right- 

 hand salpa, and it will be seen that they are exactly as they are repre- 

 sented in cut W at 28. 



The right half of the pharynx is joined by a short tube, 27, to the 

 right side of the endodermal tube, d', while the oral and aboral ends of 

 the left half of the pharynx have no communication with each other 

 except through the tube, 28, which passes around the stolon, and con- 

 nects with the left side of the endodermal tube. The left half of the 

 endostyle d 2 bends over onto the far side of the axial tube, as is shown at 

 d 2 in Plate XL, Fig. 14, while the right half d' remains parallel to the 



