INVERTEBRATA, CRYPTOGAMIA, MICROSCOPY, ETC. 627 



in diameter. The vagina lias strong circular muscles, and is divided 

 transversely by a constriction ; the only accessory organs observed are 

 three small globose vessels, situated on each side of the vagina, and 

 consisting of a distinct membrane apparently with a cellular epithe- 

 lium. Of the male organ the two testes form the chief part, and 

 consist of plicated tubes with their walls, and contain several 

 chambers lined with flat polygonal cells, enclosing a mass made up of 

 small nucleated cells, apparently the sperm-cells. Two short, wide 

 vasa defereutia, lined by circular muscles, underlie the testes. The 

 medially placed ductus ejaculatorius, of similar structure, is about 

 twice as broad, and terminates in a copulatory apparatus of the form 

 of a bulb witb a hollowed chitiuous ridge, with two chitiuous hoojis at 

 its sides, ending in a sharp, transparent, barbed point ; the muscles 

 arc transversely arranged. The long, narrow accessory glands observed 

 by Treviranus open into the distal end of the ductus ejaculatorius ; 

 they are difficult to disentangle from the surfiice of the testes, and 

 are lined by an epithelium of roundish or cubical cells and by a fine 

 membraua intima. 



5. Crustacea. 



Central Nervous System of the Crayfish.* — Herr Krieger 

 appears to have a very high opinion of the usefulness of osmic acid, 

 which he ordinarily applies thus : The ganglia having been removed 

 from the crayfish, are placed on a slide over the mouth of a wide- 

 necked flask containing the acid. After having been thus subjected 

 to its vapour they are removed to picrocarmine, in which they remain 

 for twelve hours ; they are then macerated in very dilute picrocar- 

 mine, to which a little picric acid has been added. This treatment is 

 best aelaptcd for the demonstration of the nuclei, and the protoplasm 

 of the ganglionic cells. After entering into the mode of investigation 

 in further detail, the author passes to the descriptive portion of his 

 paper; this falls under two heads: (1) Histological, and (2) Topo- 

 graphical. 



(1) Commencing with an account of tlie ganglionic cells of the 

 central nervous system, the author says that they are in all cases 

 destitute of a membrane, are more or less sj^herical or pyrift)rm in 

 form, and provided with a proportionately largo and spherical nucleus. 

 The following forms may be distinguished : — 



a. Cells with distinct protojilasm, and generally with a number of 

 nucleoli within the nucleus. 



b. Small cells with a delicate fringe of protoplasm, which is most 

 distinct in the neighbourhood of the process given off from the cell. 



c. Very small granular elements, with processes ; the protoplasm 

 is evanescent ; the fine, granulated, cell-contents are highly refractive, 

 but there are no evident nucleoli. 



Tlie fibrous elements maybe divided into those which belong to the 

 ganglionic processes, to tlie fibres of the transverse or of the longitu- 

 dinal commissures, or to the perijiheral nerve-fibres; histologically, 

 they may be said to be tubular and well ilevelopeil, or fibrillar and 



* 'Zcitsclir. wis8. Zonl.,' xxxiii. (18S0) p. r)27. 



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