AMPHIOXUS LANCEOLATUS. 
407 
PLATE XXXVI jB. 
Eig. 1. — Transverse section of a “primary bar” of the pharynx of 
Amphioxus. 
Pig. 2. — Transverse section of a “tongue bar” of the pharynx of 
Amphioxus. 
Letters in Pigs. 1 and 2. — al. Left inner epithelial band. ar. Right inner 
epithelial band. nm. Median inner epithelial band. col. Columnar lateral 
cells, with long cilia, n. Superficial nuclei. »' . Deeper nuclei (? all epithelial 
or some mesoblastic). sept. Clear septal tissue. Bl. vess. Supposed blood- 
vessel, connected in the primary bar with the lateral branches of the median 
endostylar artery, and ending blindly at the ventral extremity of the tongue 
bars ; probably connected dorsally iu both to the dorsal aortas. Rod. The 
chitinoid skeletal rod, bifid in the primary bar, hollow iu the tongue bar. 
fiss. Fissure, due to the bilateral origin of the rod of the primary bar. x. 
Sporadic cavity of the rod of the tongue bar. Coelom. The coelomic cavity 
occupying the pharyngo-pleural extension of the primary bar, but enclosed in 
the rod of the tongue bar. Ccel. ep. Coelomic epithelium of the pharyngo- 
pleural pouch of the primary bar. air. epith. Atrial epithelium (epidermic), 
clothing the external face of both bars. pig. Lateral groups of pigment in 
the atrial epithelium of both bars. 
Fig. 3. — a. to e. Various forms of the chitinous substance of the tongue 
bar, as seen in transverse sections, f. to h. Various forms of the chitinous 
substance of the primary bars. 
Pigs. 4 to 9. — Six consecutive vertical sections across the endostyle of the 
anterior third of the pharynx of Amphioxus. The sections are numbered from 
behind forwards. The first section (Pig. 4) passes on the side marked “ Right,” 
through the junction of the anterior half of the fork of the rod of the 
primary bar A with the posterior half of the fork of the rod of the primary 
bar B. Opposite to this, on the side marked “ left,” the section traverses 
the actual fork of the rod of the primary bar C, at the point where a lateral 
vessel is given off from the median endostylar artery, and runs up into the 
fork (see Schneider’s figure of the bars and blood-vessels, loc. cit.). The 
grouping of the epithelial cells is shown in all the figures; they are lettered 
in Pig. 9 as follows : — al. and ar. Right and left lateral epithelium (similar to 
that marked al., am., ar., in Pigs. 1 and 2). bl. and hr. Right and left groups 
of less-staining cells, cl. and cr. Right and left interposed groups of darker- 
stained cells, dl. and dr. Mediad right and left groups of less-staining cells. 
m. Median group of darker-stained cells, with a special very long tuft of 
cilia. In all nine groups of cells. 
In all the sections the chitin-like endostylar plates, immediately underlying 
the nine-zoned endostylar epithelium, are seen ; like the chitinoid substance 
of the pharyngeal rods they are coloured yellow, having a slightly yellow 
