158 WILLIAM BLAXLAND BENHAM. 
tissue. dv. Blood-vessels. cz. Circular muscles lying internally to longi- 
tudinal muscles (/g.). cu. Cuticle. ep. Epidermis. /. Ligament connecting 
stomach with body wall. p. Terminal pit. 
Fie. 36.—A series of six transverse sections, selected from a series in order 
to show the arrangement of the mesenteries and chambers; all are close 
together, from the oral region of the body, and are slightly diagrammatic. 
A is the uppermost, and passes through the dorsal origin of the trans- 
verse septum (S,), which passes obliquely downwards, so that here 
only the supraseptal (s. s.) ccelom is present. 
B. The septum is passing between rectum and cesophagus, the infraseptal 
(z. s.) chamber lying to its left ; to the right is the supraseptal (s.s.) 
chamber. ‘The lateral mesenteries are just appearing, and the 
cesophageal and rectal chambers communicate by means of the 
nephridial funnels (/). 
In C (which is three or four sections onwards) the lateral mesentery (/. m.) 
divides the cesophageal (@. c.) from the rectal chamber (7. ¢.), and 
the smaller funnel is no longer present. 
In D and # the septum stretches further and further across the ccelom, 
the supraseptal chamber is smaller, whilst the cesophageal chamber 
is increasing in size. 
In F only a very small portion of the supraseptal chamber is seen on one 
side. The two lateral mesenteries (/. mw.) are now thinner. The 
other mesenteries, rectal and esophageal, do not begin till further 
down. 
