ZOOLOGY AND BOTANY, MICROSCOPV, ETC. 429 



receives an explanatory hint as to its causation, from the idea of an 

 originally independent and colonial constitution.* 



Ear of Ganoids.! — Herr A. Cisow has studied the structure of the 

 organ of hearing in two species of sturgeon, besides the sterlet. His 

 figures are taken chiefly from the latter. He sums up his results as 

 follows : — 



1. The membranous labyrinth essentially resembles that of osseous 

 fishes. This resemblance extends to microscopic details. 



2. The endolymi^hatic duct arising from the sacculus runs into a 

 csecal endolymphatic sac. In the Plagiostomi, as both Weber and 

 Eetzius have shown, canals proceed from this sac towards the surface 

 of the skull. 



3. There exist papillcB partis basilaris, like tliose discovered bv 

 Eetzius in osseous fishes. 



4. The author does not share the views of his predecessors as to 

 the structure of the wall of the labyrinth. Hasse, Eetzius, and Kuhn 

 describe its tissue as fusiform cartilage {Spindelknorpel). He compares 

 it to the cornea, like which it has juice-passages, and within these a 

 reticulum of protoplasmic bodies. The ground-substance contains 

 connective-tissue fibrils, best displayed by means of trypsin-digestion. 



5. The neuro-epithelium is similar on all the cristce and maculcB 

 acusticce, as well as on the papillce partis basilaris. It is monoderic, 

 and consists of two kinds of cells, difiering in form. The cylinder- 

 cells lie between the peripheral processes of the fibre-cells. The 

 cylinder-cells have granular protoplasm ; about the region of the 

 oblong nucleus, with its brilliant nucleoli, the cell is somewhat in- 

 flated. The surface of the cell often displays a fine longitudinal stri- 

 ation. The free ends of these cells are often protected by a clear 

 cuticular selvage, stretched continuously from cell to cell. From this 

 border, just above the middle of each cell, arises a long auditory hair, 

 having a broad base, and tending to become resolved into fibres 

 towards its point. The inward opposite extremity of the cylinder- 

 cell extends to about half the depth of the ejiithelial layer, where it 

 usually ends abruptly. As to the fibre-cells, their form differs accord- 

 ing to the position of the nucleus. If the nucleus lie midway in the 

 cell, the latter is fusiform : this is M. Schultze's fibre-cell, with peri- 

 pheral and central processes. The peripheral process reaches to the 

 cuticular border ; the central process has its somewhat expanded end 

 inserted on the basal membrane of the wall of the labyrinth. If the 

 nucleus lie towards the deeper end of the fibre-cell, the conical body 

 of the cell rests directly upon the basal membrane. These cells have 

 but one (peripheral) process, and answer to M. Schultze's basal 

 cells. As with the other cells, this process extends to the cuticular 

 border. 



6. The nerve-fibres enter the epithelial layer, either as axis-cylin- 

 ders protected by their sheath, or they retain at first Schwann's sheath 

 together with the medullary sheath. Without dividing, they pass by 



* Cf. also M. Perrier's remark3,'this Journal, iii. (1880) pp. .^92. 

 t Arch. Mikr. Anat., xviii. (1880) pp. 486-519 (2 pis.). 



Sf-r. 2.— Vol. I. 2 Q 



