Literary Notices. Ixv 



to other organs, a supplementary nerve-supply from the adjacent integu- 

 mentary nerves arising from the pleural ganglia; and (3) this supplement- 

 ary supply, while remaining subordinate in Facclina, may in other forms 

 have gradually come to supplant the original epipodal (pedal) nerves, 

 which (on this view) have now completely disappeared in such forms as 

 Polycera and Aiicula, and are only represented in Dendronotus by the 

 pleuro-pedal anastomosis. This is however only a suggestion which we 

 do not feel able to support or press further at present." — [C. H. T.] 



Nervous System of Pentastomum Teretinsculuv. 



In his late paper on the Anatomy of Pentostomum teretinsculuml 

 Mr. W. Bald\vin Spencer devotes a few pages to the nervous system. 

 The following is a brief summary of those pages : 



There is a large double subcesophagal ganglion, which gives origin 

 to nine pairs of nerves ; but this is no supraresophagal ganglion. How- 

 ever a commissural ring extends from the subcesophagal ganglion around 

 the oesophagus. In this subcesophagal nerve-mass the whole of the ven- 

 tral chain is concentrated; and from it nerves pass to all parts of the 

 body. Histologically this nerve mass consists of an inner cord of fibres 

 surrounded by a shell of nerve cells. These cells are more numerous at 

 the origin of the nerves than elsewhere. As a rule the cells are pear- 

 shaped and give origin to but one fibre; but in rare cases two or even 

 three processes arise from the same cell. At the origin of the nerves and 

 all along the posterior cords may be seen thin elongated cells which have 

 been pulled out in the direction of the branch. 



Sense Organs. — In the female there are present eight, and in the 

 male nine pair of sensory papillae. Two are much more prominent than 

 the others and have been called by Leuckart, " Tastpapillen." The 

 tastpapillen and a few other papilla? undoubtedly contain end-organs. 

 It is not certain what the function of these papillae is. Probably they 

 function as tactile organs, keeping the parasite informed as to the condi- 

 tion of the blood supply in its host. — [C. H. T.] 



Primitive Segmentation of the Vertebrate Brain. 2 



Mr. Waters thinks that the fore-brain is composed of at least two 

 well-marked neuromeres, from the first of which the olfactory nerve arises 



1 . Quart. Jour. Micro. Sci., Vol. XXXIV, part I. 



2. Waters, Bertham H. Quat. Jour. Micro. Sci., Vol. XXXIII, p. 4.57-47t) ; pi. 



