AMPHTOXUS LANCEOLATUS. 
377 
tion of the pharynx ; in larger specimens they are seen in 
sections coincidently with a full series of bars and slits as in 
Plate XXXVI. 
The independent metamerism of the body wall on the one 
hand, and the gill-slits on the other in Amphioxus, is a matter 
of some interest in relation to the metamerism of musculo- 
skeletal axis and branchial bars in craniate Vertebrata. 
The Spaces Enclosed in the Body of Amphioxus. — There are 
three distinct kinds of spaces containing liquid in the living 
state, which are to be met with in the study of transverse sec- 
tions of Amphioxus. These are : (1) the atrial cavity; (2) the 
enteric cavity ; (3) hsemo-lymph cavities. The last group is 
divided into several sections which are more or less distinct 
from one another ; they are (a) the vascular system, which, as 
shown by Schneider, is in open continuity with ( b ) the supra- 
pharyngeal and perienteric portions of the coelom ; (c) the 
perivascular spaces of the dorsal aortse ; ( d ) the perigonadial 
coelom; (e) the right and left metapleural lymph-spaces ; (/) 
the lymph-spaces of the dorsal and ventral fin-rays ; (g) the 
superior and inferior intra-notochordal lymph canals; (A) 
the neuraxial canal ; (t) the myoccelomic pouches or intra- 
muscular lymph-spaces of the head ; (A) the series of intra- 
skeletal lymph-spaces of the myotomes. 
As has been mentioned above, it is extremely difficult to 
arrive at a correct conclusion as to the existence of spaces 
within the body of Amphioxus, owing to the distorting action 
of the reagents used for hardening specimens before cutting 
sections. The chief errors which have been made by previous 
writers — some falling into one mistake and some into another 
— are the ascription to Amphioxus of a single wide ventral sub- 
epidermic lymph canal, or of a series of such canals beneath 
the plaited ventral region of the branchial chamber, the denial 
of the existence of natural canals in the metapleura, the over- 
looking of the intra-notochordal lymph channels, and the 
assertion of a canalicular communication (“ godets ” of 
Moreau) between the contents of the notochordal sheath and 
the space enclosed by the superjacent, neuro skeletal tube. 
