ZOOLOGY AND BOTANY, MICKOSCOPY, ETC. 715 



hand, no unstriped muscle-fibres seem to occur ; while the most mobile 

 organs of molluscs, the arms, the siphon, the heart of Cephalopods, the 

 fins of Pteropods and Heteropods, do not include any truly striped 

 fibres. But all Molluscs are not without striped muscle, for this may 

 be seen, as E. Blanchard observed, and as the author confirms, in one 

 portion of the adductor muscle of Pecten. In Lima also, striated fibres 

 were seen. 



MoUusca. 



y. Gastropoda. 



Comparative Histology of Glandular Epithelium of Kidney of 

 Prosobranch Gastropods.* — M. E. Perrier, who has already described 

 the structure of the kidney in Littorina, now enters on a comparison 

 between various allied forms. He finds that in some of the lower' 

 Prosobranch s, such as Fissurella, the epithelial cells are not so much 

 differentiated as in the Limpet. As Haller has shown, the cells are all 

 of the same kind, and all glandular and ciliated, but they difi'er both 

 from the ciliated and from the vesicular cells of the higher Monotocardia, 

 for they are large, and have no excretory vesicles. Sometimes they con- 

 tain no concretions, while at others they are so loaded with them that the 

 nucleus is invisible. The epithelial investment is of an almost diagram- 

 matic regularity ; the elements are clearly all of the same age, and one 

 cannot distinguish between cells that have performed and others that 

 are about to perform their function. Secretion appears to be effected by 

 osmosis, but if the production of renal material becomes exaggerated, it 

 is deposited in the form of small granules in the interior of the cell. 

 There is no absolute line of demarcation between granular and vesicular 

 cells. 



A very dijfferent arrangement obtains in the higher T^nioglossata, 

 such as, for example, Cassidaria. The structure of the kidney is here 

 extremely complex. Instead of the simple lamellae found in Littorina, 

 there is a complicated network of connective trabeculte ; these are 

 hollowed by blood-lacuufe, and invested with a continuous epithelial 

 layer. The whole forms a thick spongy mass which leads the author to 

 propose the term of " glande hematique." The free surface of this mass 

 is grooved by afierent vessels, and the epithelial layer is differentiated 

 in a remarkable way. In addition to the numerous ciliated elements, 

 there are glandular cells, which have not, however, the ordinary 

 appearance of the vesicular renal cells which abound in the deeper parts 

 of the mass. The vacuole is not clear, nor does it contain a solid con- 

 cretion, but is loaded with granulations which take a blue colour with 

 methylene. They have all the characters of mucus-cells. 



The numerous intermediate types found in the kidney of the Gastro- 

 poda will be described in a detailed memoir. The author differs from 

 M. Garnault in his interpretation of the structure of the kidney of 

 Valvata and Cyclostoma. He is further convinced of the accuracy of 

 his views as to the mechanism of the secretion of the vesicular cells, but 

 he does not, of course, mean that the renal cells are eternal ; like the 

 cells of all glands they become w^orn out and absorbed, but there is no 

 direct connection between the secretion and the death of the cell. The 

 gentian-violet used by M. Garnault has not a sufficient selective power ; 



* Comptes Rendus, evii. (1888) pp. 188-91. 



