-35- 



Fig, 6 h shows the most posterior of the four sections 

 passlnp through the coil. It presses through the point where the 

 median cell-f^roups (m.c.g.) make their first bend dorsalward 

 to where they turn again to form the anteriorly directed whorl 

 (in. eg'.). 



As has been previously said, the lateral cell-groups 

 (l.o.g.) t^^ke no part In the posterior coll but extend for a con- 

 siderable distance posterior to the coil, somewhat diminished 

 in size, and gradually approach each other until they are in 

 close contact. . ■ 



Fig. 6 i represents a section taken at a point about 

 midway between the extreme posterior end of the gland and the 

 posterior surface of the coil. It shows the two pairs of lat- 

 eral cell-groups (l.c.g), each with its characteristically curved 

 lateral ciliated charat.er (l.c.h.). Just posterior to the coil 

 the two large pseudobranohial arteries, which were seen on each 

 side of the gland in all the preceding sections (Figs. 6 a-h, 

 art,), unite to form the one large artery Been in Fig. 6 l,art. 

 lying between the gland below and the ciliated groove above. 

 This artery is very large, being almost as great in cross section 

 as the end of the thyroid below it. The wall of the pharynx 

 is separated from the gland >'y a comparatively small space, so 

 that it is evidently pushed upward by the large coiled end of the 

 gland and sinks down again just behind this elevation. The groups 

 of gland cells -'ave diminished somewhat in cross section, but they 



