INVEKTEBRATA, CRYPTOGAMIA, MICROSCOPY, ETC. 767 



tliero are slight projections, and tliese give rise to tlio parapodia, 

 which aid in forming a kind of funnel-shaped orifice. Just behind 

 the mouth there is a short, eversible proboscis, and connected with 

 this there is the obscure structure which is known as the buccal 

 bulb ; this somewhat elongated organ is ovoid in general shape, and 

 has behind the two swellings with which it is provided a cylindri- 

 cally shaped prolongation, which is the seat of origin of the radula. 

 The muscles of this bulb are, consequent on the absence of any 

 chitinous skeleton, exceedingly well developed; chitinous parts are, 

 however, developed from the epithelial cells of the bulb, and at onco 

 become sufficiently strong to form two small resisting plates, which 

 may well be regarded as rudimentary jaws. These have an interest- 

 ing structure ; they are made up of a number of small, irregularly 

 cylindrical rods, closely set and all directed towards a common 

 central point. That they are rudimentary jaws would appear to bo 

 sufficiently well established by the comjiarison which the author has 

 instituted between them and the similar structures of a further 

 grade of development which are to be found in Bulla and in other 

 allied genera. In addition to these rudimentary jaws, small chitinous 

 papillas have been detected at the point where the proboscis passes 

 into the bulb. The support for the radula occupies the base of the 

 buccal cavity ; the radula itself forms a band which is twice as long 

 as it is wide, the central portion is unarmed and only presents some, 

 always small, chitinous granules or concretions. On either side there 

 is a longitudinal row of well-developed teeth, and on these there 

 follow five parallel rows of smaller lateral teeth (uncini). 



The oesophagus takes a course a little towards the left, and then 

 descends to a somewhat lower plane, where it passes into what the 

 author calls the second cavity of the body ; it becomes at once con- 

 tinuous with the stomach. This poi'tion of the tract, in which no 

 gizzard seems to be developed, is enveloped by the " hepatico-herma- 

 phrodite mass " ; the internal epithelium is provided with a number of 

 short cilia. As an ordinary rule, there open on its surface ten distinct 

 hepatic orifices. The walls of the intestine are even more delicate 

 than are those of the stomach, and they have no proper coloration ; 

 what they have is due to their contents. This region, somewhat 

 equal in calibre to the oesophagus, is not dilatable ; after some coiling 

 it ends on the right side, in a little pit behind the respiratory appa- 

 ratus. Towards its termination the musculature of its walls becomes 

 better developed ; Foraminifera, Eadiolaria, and diatoms appear to 

 form the chief food of these molluscs. 



The salivary glands form two long, white, hyaline sacs without 

 ramifications, and placed one on either side of the rosophagus, which 

 they follow along its course, although without contracting any con- 

 nection with it, and they open into the buccal cavity by narrow ducts, 

 just above the ccsophagus. The glandular layer is formed of two 

 rows of cells, of some size but irregular in form ; their nucleus is 

 distinctly visible. 



The liver, contrary to what obtains in most of tlic Opistho- 

 brancliiata, is not compact, nor docs it open into the stomach by 



