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Transactions of the Boyal Society of South Africa. 
is already a high degree of differentiation of the olfactory capsules (Fig. 8). 
There is an almost straight wide tube leading from the external nares (E) 
to the mouth cavity (M) ; into this the two chambers of the capsule open 
and the posterior end of the anterior chamber (AC) opens into Jacobsohn's 
organ, which in turn communicates with the mouth (MI). 
The Xenopus tadpoles, as already remarked, have no horny jaws and 
the section passes through its anterior end. Notice that both grooves 1 and 2 open into the 
opercular cavity EC ; these openings are irregular and situated at the posterior ends of the 
grooves, W is a portion of the groove 1, which passes backwards beyond the external 
opening (OE in Fig. 7) and is filled with foodstuff kept back by the sieve-like respiratory 
tissue. Each V-shaped groove contains two cavities — the intra-pharyngeal {e.g. W) and 
an extra-pharyngeal situated below the " sieve " ; the latter is supported by irregularly 
arranged bars of cartilage. M = portions of membranous labyrinth ; Me = medulla 
oblongata ; Di = diencephalon ; 0 = optic lobi ; CP = choroid plexus; B = blood-vessel. 
their method of feeding is therefore different to that of frog tadpoles. 
Instead of browsing on algal filaments they hover near the bottom of the 
vessel containing them, their mouths being near the bottom and the tails 
pointing obliquely upwards. In this position they perform continuous, 
rhythmic swallowing movements, and so ingest the minute protozoa and 
algae living on the bottom. It seems that they need principally an 
