CURRENT LITERATURE. 67 



ANATOMY. 



On the Innervation of the Cerata of some Nudibranchiata. (Quart. 



Jour. Micros. Sci., xxxiii. pp. 541-558, pi. 32-34, 1892.) 



There has been considerable controversy of late in regard to the nature of the 

 so-called epipodial processes of the Rhipidoglossa. Lacaze-Duthiers and others 

 of his school have denied their right to be regarded as pedal structures, and have 

 regarded them as pallial outgrowths, innervated from the pleural ganglia. 

 Pelseneer has disproved this statement, however, and has shown conclusively 

 that the processes in question are supplied by epipodial nerves, which arise from 

 the pedal ganglia. 



It is still a moot point whether the dorso-lateral ridges and processes of 

 Opisthobranchiate Mollusca are homologous with the epipodia of the Rhipido- 

 glossa, or whether they are not rather to be regarded as structures s/ti generis (the 

 " pleuropodia " of Garstang). In the present paper, Prof. Herdman and Mr. J. 

 A. Clubb have endeavoured to solve this problem by investigating the nerve-supply 

 to the processes (cerata) in several different types of Nudibranchiata. They arrive 

 at negative results upon the main point, owing to the remarkably different modes 

 in which the innervation is effected in different sections of the group ; and they 

 conclude that the nerve-supply cannot be taken in this case as a sure indication 

 of homology. The following are the modes of innervation established. 



In Polycera and Ancitla (Holohepatica) the nerve-supply is entirely derived 

 from the pleural ganglia, except that in Polycera there is a small accessory nerve 

 on the left side which springs from the pedal ganglion, according to Alder and 

 Hancock. In Herman (Ascoglossa) the innervation is also entirely from the 

 pleural ganglia. In Dendronotus (Cladohepatica) the cerata are innervated on 

 each side by two nerves, one of which is entirely pleural in nature, while the 

 other contains a pedal element (cf. the similar pleuro-pedal cervical plexus 

 described by Pelseneer in gymnosomatous Pteropods and Aplysia). In Tergipes 

 (Cladohepatica) the innervation is entirely from the pedal ganglia ; as it is also in 

 Facelina (Cladohepatica), except for the existence of a small accessory pleural nerve 

 on the left side, which supplies only the most anterior clump of cerata. 



The authors regard the innervation from the pedal ganglia only ( Tergipes) as 

 the most primitive condition, and suggest that this arrangement has been 

 secondarily supplemented (Facelina, Dendronotus) or entirely replaced (Her/iuea, 

 Ancitla, Polycera) by innervation from the pleural ganglia. 



On the Eyes of the Mollusca. (Arch, de Biologic T. xii., pp. 57 — 150, 

 pits, iii — v.) 

 M. Victor Willems' memoir is most interesting. The terrestrial Pulmonata 

 guide themselves principally by their sensation of touch. The distinct form of 

 objects can only be distinguished at a distance of from I to 2 mm., while 

 a confused image is obtained at a distance of a centimetre. All the Pulmonate 

 Gastropods, both those which can and those which cannot see, have dermatoptic 

 perceptions. They cannot perceive ultra-violet rays, but all are sensible of 

 different degrees of light, while a rapid change produces a greater sensation of 

 fear in freshwater than in terrestrial forms. Cyclostoma sees better than any of 

 the marine Prosobranchiata, and is therefore regarded as being near to the 

 terrestrial Pulmonata. 



On the Nervous System of Heteropods. (Comptes Rend., cxiv., p. 775, 

 1892.) 

 M. P. Pelseneer gives an account of his studies on the nervous system of 

 a number of Heteropoda. The pleural and cerebral ganglia are fused and the 

 visceral commissure crossed. He is of opinion that generally the nervous system 

 agrees with those streptoneural Gastropods, which are most closely allied to the 

 Heteropoda. The Heteropoda are modified Prosobranchs, the external modifi- 

 cations being largely due to their pelagic life. 



On the Reproduction of the Dart. (Jy. Conch., p. 33, 1892.) 



Mr. R. Standen during an attempt to breed from a sinistral specimen of 

 H. aspersa, has made some interesting notes on the reproduction of the Dart, 

 which fully confirm the observations of Perez, Collinge, and others, that this organ 

 is re-formed in from five to seven days. 



