ZOOLOGY AND BOTANY, MICROSCOPY. ETC. 933 



Classification of Gastropoda by the Characters of the Nervous 

 System.* — Dr. P. Pelseneer has some critical remarks on the attempt 

 made by Prof. Lacaze-Duthiers to arrange the Gastropoda by the cha- 

 racters of their nervous systems. He regrets that that anatomist did not 

 include in his scheme the Amphineura, Heteropoda, and Pteropoda. It 

 seems unnecessary to give new names to groups whose boundaries remain 

 unaltered. Various instances are cited in which animals have not the 

 anatomical disposition of parts which is assigned to the group to which 

 they belong. The five " orders " of M. Lacaze-Duthiers do not appear to 

 be of the same systematic importance, and that of the Notoneura does 

 not seem to be natural. M. Pelseneer thinks that the imperfections of 

 the new system are due to the inexact interpretation of the morpho- 

 logical value of the pleural ganglia which falsifies the very basis of the 

 system. These ganglia do not belong to the visceral commissure, that 

 is to the asymmetric centre, but to the anterior symmetrical group of the 

 nerve-centres. Moreover it is easy to show that the pleural ganglia do not 

 fuse with the asymmetric or visceral centres, while they often do fuse with 

 one or other of the two anterior pairs. 



Structure and Development of Egg in Chitonidse.f — Dr. P. Garnault 

 differs from Prof. Sabatier in his account of the development of the egg 

 in Chitonidse. He finds that the egg is developed at the expense of the 

 germinal epithelium which lines the ovary ; the membrane which sur- 

 rounds it is always composed of nucleated cells, formed by the trans- 

 formation of sister-cells of the ovum ; this membrane may be called 

 follicular, and it is, contrary to the opinions of Ihering and Sabatier, 

 the only one which is ever formed round the egg. The author finds that 

 the inclosing vitelline masses do not take any part in the formation of 

 the nuclei of the membrane. An account is given of the expansion and 

 retraction of the vitelline masses; these may be considered as the 

 highest known expression of the faculty, possessed by all eggs, of 

 emitting amoeboid expansions. The author also describes in some 

 detail the characters of the membrane of the ripe egg. 



Organization of Lentalium.J — Dr. L. Plate has been induced to 

 study Dentalium by the suggestion of Grobben that the Scaphopoda are 

 the ancestors of the Cephalopoda. The glandular cells on the margin 

 of the mantle are of extraordinary length, and are swollen out at either 

 end. They are succeeded by a layer which seems to be formed of a kind 

 of gelatinous tissue, delicate connective-tissue and muscular filaments 

 lying radially and vertically in a hyaline ground-substance. Further 

 back the mantle-zone becomes quite muscular. On the inner edge there is 

 again a well-developed glandular zone, the elements of which have the 

 form of short flasks. Between it and the outer muscular ring there is a 

 system of irregular blood-lacunse. The muscles consist of rounded smooth 

 bundles of fibrils ; each of these is invested by a delicate membrane ; the 

 elongated nuclei lie below this membrane and externally to the fibrils. 



The author does not agree with Lacaze-Duthiers in regarding the 

 elongated swellings which lie outside the cerebral ganglia as secondary 

 appendages of these centres, but as independent ganglia which are con- 

 nected by two commissures, on the one hand with the brain and on the 

 other with the pedal ganglia. Dr. Plate thinks there is no doubt that 



■^ Bull. Soc. Zool. France, xiii. (1888) pp. 113-5. 



t Arch. Zool Expe'r. et Gen., vi. (1888) pp. 83-116 (2 pis.). 



% Zool, Aozeig., xi. (1888) pp. 509-15. 



