162 ARCHICGLOMATA. 
collar pores) lead out from the collar at its hind end. 
In the front region of the trunk, opening dorso-laterally 
into a long dorsal groove, there are two rows of small 
- slits which open downwards into the alimentary canal. 
They are numerous and are known as the pharyngeal 
clefts. Tying outside the pharyngeal clefts, and also con- 
tinued backwards behind them, are two rows of genital 
pores. 
Fig. 94.—SEMI-DIAGRAMMATIC VIEW OF BALANOGLOSSUS 
FROM THE DoRSAL SURFACE. 
Proboscis. 
Collar. 
Trunk, 
Hepatic Glands. 
Openings of 
onads. 
The ectoderm consists of a simple ciliated epithelium 
with unicellular mucous glands. 
The mouth leads into an elongated pharynx. The 
extreme anterior wall of this pharynx is pushed forwards 
into the proboscis as a diverticulum, the szd- 
BUMRET: a oural gland.* The epithelial cells, forming 
the wall of this organ and that of the anterior part of 
the pharynx, are metamorphosed into chordoid tissue (see 
Chapter XXIV.). Their protoplasm is almost entirely re- 
placed by vacuoles with walls and scattered nuclei, amongst 
which there may be small glands. This structure converts 
* This organ is also known as the ‘‘ notochord” or ‘‘ stomochord.” 
