ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 985 



" Is it, therefore, necessary to admit that that which a section does not 

 show does not exist? is this not exaggeration? for often, very often, 

 it is very difficult, if not impossible, to light on certain special points 

 of an organ which one is cutting, and consequently to see arrange- 

 ments which may escape the razor, but which do not tlie less exist." 



Prof, de Lacaze-Duthiers justifies the term of Soleuoconchs which 

 he has proposed for the group of which Dentaliam is the representative, 

 and objects to those of Scapho^^oda and Cirribrauchiata which are 

 based on erroneous views. 



Anatomy of Fissurella.* — M. L. Boutan communicates the results 

 of an anatomical investigation of the alimentary canal, the organ of 

 Bojanus, and the reproductive organs of this Gastropod. 



(a) Tlie alimentary canal agrees with that of Ealiotis in having an 

 anterior mouth with two "jaws" and a radula, an oesophagus with 

 voluminous lateral diverticula, a stomach with three distinct regions, 

 a lining of cilia throughout, except on the stomach walls, and a rectum 

 traversing the heart and opening on the dorsal surface between the 

 gills. There are, however, only two radular cartilages instead of 

 fuur, the two first oesophageal diverticula are absent, and the other 

 two, which were always empty and provided with well-developed 

 double valves and with internal ramified glands of great delicacy, 

 seem to be purely digestive in function, and incapable of affording 

 lodgment for the food. The anus lies on the median line on a level 

 with the opening of the organ of Bojanus ; the liver has two lobes 

 united on the ventral surface of the stomach and discharges its pro- 

 ducts by several orifices into the first stomachic region ; the salivary 

 glands are arborescent tubes, and there are two other organs in the 

 mouth also with ciliated cells and probably representing an anterior 

 pair of salivary glands. 



{h) The organ of Bojanus is median in position, with a larger 

 right lobe. Anteriorly and dorsally it adheres to the floor of the 

 branchial cavity and extends almost to the oesophageal diverticula. 

 In its median portion it divides into two lobes, following the contour 

 of the pericardium, covering the dorsal surface of the liver, while its 

 inferior right portion extends to the level of the genital gland. It 

 opens along with the generative ox-gans to the right of the anus. A 

 single layer of large cubical cells, with very large nuclei and with 

 yellowish granules, lines the various cavities of the gland. 



(c) The reproductioe organs. — The crescentic sac of the ovary lies 

 iiiferiorly, witli a superior surface intimately embracing the liver, and 

 resting hitcrally on the foot and epipf)diuni. The essential portion 

 consists of stalked cells, each forming an ovum, and originating on the 

 wall oi the gland not in contact with the liver. From the right side 

 of the ovary a loose delicate duct leads to the common excretory and 

 generative aperture. On the wall of this oviduct a whitish albumen 

 gland with huge ciliated cells is readily distinguished. In the mature 

 state the two sides of the ovary have increased greatly in size, 

 U8ccuding each side of the body, compressing the liver and ali- 



♦ Coini.tes IJcn.luSj ci. (1885) iip. 388-91. 



