of the skin. It shows the anterior extension of the dorsal myotomes 
(III, IV) and the dorsal region of the basilaris (VJ) extending under 
the dorsal myotomes, in addition to the other structures labelled. Among 
these other structures are a few of the curious glandular masses (R, 
S, T, U, W, Y, Z) which I have also shown in figures 27 and 28. 
In figure 25 two paired glands (R, T) and one median gland (S) 
are to be seen.!) One pair (R) is situated towards the sides on the 
anterior region of the anterior dorsal cartilage and are flat circular 
bodies. The other pair (7) are small rod-shaped bodies situated at 
the sides of the head just behind the buccal funnel and below the 
edge of the anterior dorsal cartilage. The unpaired gland (S) is a 
minute spherical little body possessing a stalk situated anteriorly 
(though behind the paired glands R) in the mid-dorsal line of the 
anterior dorsal cartilage.) The histological structure of these glands 
(and of the others shown in fig. 27) is similar throughout (fi.g. 26). 
Each consists of an outer connective tissue investment or tunic, enclo- 
sing an inner layer of glandular cells, which themselves surround a 
central mass of granular secretion material. I have not ascertained 
the mode of vascular supply. I have seen no trace of a duct. It is 
probable that these glands are among those described in Cyclostomes 
by Hertwie (45) but this I do not know. 
In figure 27 the posterior dorsal cartilage has been removed, 
also the first two segments of the dorsal myotomes, the dorsal portions 
of the basilaris muscle, and the sub-branchial musculature and other 
ventral structures anterior to the eyes on both sides. The result is 
the exposure of the pharyngeus musculature and three more paired 
and one median unpaired glandular masses (U, W, Y, Z). The 
pharyngeus musculature (XX) has been well described by P. FÜRBRINGER. 
Briefly speaking it consists of a large tubular sheet of muscle sur- 
rounding on all sides, and dorsally closely attached to, the wall of 
the throat cavity. At its anterior extremity it is attached on the 
dorsal side to the under anterior surface of the broad posterior dorsal 
cartilage (A.B., fig. 27); posteriorly, the hind edge is attached laterally 
to the stout styloid and cornual processes. The pharyngeus is widely 
separated from the throat cavity on all sides except dorsally (figs. 28, 
1) Another pair of glands was present but removed before their position 
was noted. 
2) In Petromyzon marinus the stalk of this median gland pierces the 
anterior dorsal cartilage and this is probably the case in Geotria. 
