REVIEW OF SPENGEL’S MONOGRAPH ON BALANOGLOSSUS. 387 
collar ccelom on each side opens by a short ciliated canal into 
the outer part of the first gill-slit. Projecting into the pro- 
boscis celom from behind we observe a spongy mass of-tissue 
with blood-vessels, Bateson’s proboscis gland, which is without 
doubt an excretory organ. Posterior to this again, is a vesicle 
(Pc.), the sac of the proboscis gland, immediately behind which 
we see the heart. This last communicates by a narrow slit with 
the great dorsal vessel. The alimentary canal commences just 
posterior to the proboscis with a ventral mouth ; its first por- 
tion in the collar region constitutes a simple buccal cavity ; the 
next part in the anterior part of the trunk bears a series of pairs 
of gill-sacs opening to the exterior by pores situated dorso- 
laterally. Immediately ventral to these openings we see the 
openings of the gonads, the sexual glands in both sexes being 
represented by a series of simple or branched sacs opening 
directly to the exterior. 
Fig. 2 on the same plate represents a diagrammatic sagittal 
section of the animal. We notice that the alimentary canal in 
the trunk region is differentiated into two tubes—a lower one 
called the cesophagus (sensu stricto), and an upper one, the 
branchial tube, into which the gill-sacs open. We notice also 
that the inner openings of these are elongated vertically, and 
almost completely divided by a projection from their dorsal 
edge, the tongue-bar ; the outer gill-pores (Brew.), on the con- 
trary, are simple circular openings. In the collar region, dorsal 
to the blood-vessel, we see a longitudinal band of tissue con- 
nected before and behind with an invagination of the ectoderm. 
This is the central nervous system, and it is connected with 
the dorsal ectoderm by three cellular strands, the dorsal roots. 
In its interior are a series of small isolated cavities lined by 
columnar cells. In the front part of the collar region a dorsal 
diverticulum of the pharynx is seen reaching far forward into the 
base of the proboscis, and underlying the heart and sac of the 
proboscis gland. Thisis the notochord; it has a cuticular 
sheath, which is largely thickened, ventrally giving rise to a 
chitinous skeletal rod. A portion of this rod is secreted by the 
inner ends of the ectoderm cells on the base of the proboscis ; be- 
VOL. 36, PART 3.—NEW SER. DD 
