100 PROGRESS OF MICROSCOPICAL SCIENCE. [^JSll^rm.! fITWo/ 



of budding. In growing, this cell pushes before it the external 

 epithelial envelope of the ovary, which thus becomes the wall of the 

 ovigerous follicle. The latter is pediculated, and the small cell 

 within it soon forms by division two new cells like the parent one. 

 This division is further jiursued once or twice on each of these, and 

 it is one of the daughter-cells of the last generation which becomes 

 the ' viable ' egg. In the ovigerous follicles one sees ovules still 

 in the rudimentary state under the forna of a small cellular group 

 situated in the inferior part of the follicle below the ovum in course 

 of its develojjment. I can do no better than compare these bodies to 

 the vitelligenous cells of insects ; both apjiear to me, in fact, to be 

 nothing less than abortive eggs, with this distinction always, that in 

 insects the cells maintain an organic union with each other and the 

 egg in course of development, whilst in the Sacculince they are either 

 free or have a slight connection with the latter. I do not believe 

 either that after the deposition of the mature ovum the little ' polar 

 cell ' remains in the ovary to become the starting-point of a new 

 ovum, as M. Ed. Van Beneden describes. It is easy to assure oneself, 

 by means of hardened preparations, that the cell has no relation save 

 with the egg to which it is adherent, and that consequently it must 

 be carried by it in its passage from the follicle, and must fall with it 

 into the ovarian sac." M. Balbiani's paper, which is of much interest 

 to comparative anatomists, then deals with the general question of 

 the primordial division of the ovum in Sacculince as pointed out in 

 the vertebrates by Pfliiger, Kolliker, and others, and also with the 

 points in relation to the second organic element (in addition to the 

 vesicle of Purkinje, which he admits the existence of in Sacculince). 

 — Comptes Bendus, December 27, 1869. 



The Afferent Canals in Clionia celata (Grant). — M. Leon Vaillant, 

 in some recent dredging excursions, has had an opportunity of study- 

 ing this curious penetrating sponge while alive and upon the oyster- 

 shell. His observations have led him to different conclusions from 

 those established by Professor Grant. He states that in Clionia celata, 

 while the papilla in the wide perforations are, as has long since been 

 shown, the oscula or efferent orifices of the water current which 

 pervade the parenchyma, the papillae of the second form are really 

 the pores of distinct afferent currents. — Paper read before French 

 Academy, January 3, 1870. 



Nitrate of Silver as an aid in Microscopic Investigations. — M. 

 Grandry has communicated to the ' Centralblatt ' the results of his 

 observations on the action of nitrate of silver on nervous tissue. He 

 used the tissue obtained from the frog and rabbit for his experiments, 

 and placed portions both from the centres and the nerves in a one- 

 fourth per cent, solution, macerating them for five days in the dark, 

 and then exposing them for three days to bright light. If the 

 surface of the cord thus treated be carefully teazed out with needles, 

 the axis-cylinders are found to exhibit a very regular and sharply 

 defined transverse striation— clear, unstained striae alternating with 

 deeply tinted ones. The breadth of the dark strife varies from one to 



