534. FRANCIS VILLY. 
of the ampulle is being separated, and it arises in the position 
where the columnar epithelium is best marked. ‘Thus it 
resembles the other parts to which the rule applies in possess- 
ing sensory cells from the first, whilst it differs from them in 
not having a sense-organ distinct from that destined for other 
parts. The ampulle and the remaining two cochlear pouches 
may be recognised by their thickened epithelium before they 
can be distinguished by their shape. 
The last division which takes place in the sensory tract 
separates it into two parts, one of which lies in the utriculus 
and one in the sacculus. It does not take place for some time 
after the others, and even in the adult these two parts are 
not far removed from each other. 
e. The Recessus Labyrinthi.—The existence of this 
peculiar organ, the anatomical relations of which have been 
described by Hasse,! has been overlooked in the Anura. The 
animals that I have examined (Rana temporaria, Bufo 
vulgaris, and Dactylethra larva) all possess very similar 
structures. Taking the adult frog as a type, the relations of 
this part of the auditory sac may be briefly noted here. A 
narrow duct leads from the sacculus near its opening into the 
utriculus, and, running up the inner surface of the vestibule, 
perforates the skull-wall. Within the skull it is dilated to 
form a large, thin walled, vascular sac, which extends some 
distance both in front of and behind the duct. The sacs of the 
two sides are connected by bands of spongy tissue above the 
cerebellum, and below the brain just behind the pituitary 
body. 
The walls are vascular, and Hasse has assigned to this part 
of the ear the function of supplying the endolymph. It cannot 
be sensory, for at no period are its walls supplied with nerves 
in sufficient quantity, and its histological structure will not 
admit of such an interpretation. It would seem to have some 
function of importance in the adult, as it steadily increases in 
size during the growth of the tadpole, and it is after the tadpole 
1 € Anatomische Studien,’ Bd. iv, Die Lymphbahnen des inneren Ohres 
der Wirbelthiere.” 
