286 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY. 



development it comes to lie far in, and its connect ion 

 with the exterior is lost. It is found finally just posterior 

 to the pleuro-pedal connective on either side (fig. 23). 



The otocysts of the two sides are bound to one another 

 by a fibrous band passing ventral to the pleuro-pedal 

 connectives, and just in front of the pedal ganglia. 

 This band is continued a short distance beyond the 

 otocysts and terminates in the dorsal surface of the foot. It is 

 probably related to the equilibrating function of the otocysts. 



The otocyst nerve passes ventral to the pleuro-pedal 

 connective and goes forward between the cercbro-pcdal 

 and eerebro-pleural connectives, fusing with the latter 

 not far from the middle of its length. Its fibres enter 

 the cerebral ganglion. The otocyst itself is a cavity lined 

 by ciliated epithelium, the cells of which are in intimate 

 communication with the underlying nerve fibres. The 

 nucleus of these cells is more voluminous than in epithelial 

 cells, and in both Patella and Haliotis the cells are smaller 

 and longer than in many other forms. The otoliths are 

 small, usually rounded and numerous ; the otocyst nerve 

 is hollow, and the otoliths may be found in its cavity some 

 distance away from the main cavity of the otocyst (fig. 27 J. 



The Ospliraclia are patches of brown-pigmented 

 epithelium, situated at the sides of the posterior part of 

 the nuchal cavity, as already stated. 



The component cells (fig. 28) are elongated and ciliated, 

 and, beneath them, we find a group of multipolar 

 ganglion cells (osphradial ganglion). In the immediate 

 neighbourhood of the osphradia, and covered by a con- 

 tinuation of this epithelium, are projections, supposed by 

 some to be the last vestiges of the ctenidia of the limpet's 

 ancestors. Their lacunae are encumbered with corpuscles, 

 and Boutan thinks they have some special glandular 

 function connected with the blood. 



