NOTES AND MEMOEANDA. 325 



portion of fresh skin, with the panuiculus adiposus attached, was 

 pinned to a piece of cork in the manner already described, and treated 

 in the same way, with the exception that this time glycerine, instead 

 of chloride of gold solution, was used for saturation. When the 

 saturated cutis tissue had been laid bare, the whole was placed in 

 glycerine, and allowed to remain in it for several days. Small portions 

 were then teased out in glycerine, stained by picro-carminatc of 

 ammonia, and examined in glycerine. In such preparations the 

 secondary bundles were found isolated, the contours of the primary 

 bundles not being preserved. In the secondary bundles the fibrillsB 

 were seen more or less distinctly, in some of them with perfect dis- 

 tinctness. 



Process for Preparing the Embryos of Fishes. — The ova of the 

 Salmonidfe are generally employed by embryologists for the study of 

 the development of osseous fishes. It is difficult to observe them in 

 the fresh state, either whole, by transmitted light, on account of the 

 thickness of their envelope, or after having opened them, in conse- 

 quence of the small consistency of the germ, especially at the com- 

 mencement of the segmentation. Chromic acid, the reagent most 

 frequently employed to harden these ova, readily alters the young 

 cells, and deforms the embryos by compressing them between the 

 unextensible envelope of the ovum and the solidified vitelline mass. 

 For the last two years M. F. Henneguy * has employed, in the labo- 

 ratory of comparative embryogeny of the College of France, a process 

 which allows the germs and embryos to be extracted from the ova 

 of Trout and Salmon with the greatest facility, and without subjecting 

 them to the least alteration. 



He places the ovum for some minutes in a 1 per cent, solution of 

 osmic acid until it has acquired a light brown colour ; then in a small 

 vessel containing Miiller's liquid, and opens it in this liquid with a 

 pair of fine scissors. The central vitelline mass, which is coagulated 

 immediately on contact with water, dissolves, on the contrary, in the 

 Miiller's liquid, while the solidified germ and cutical layer may be 

 extracted from the ovum, and examined upon a glass plate. 



By treating the germ with a solution of methyl-green, and then 

 with glycerine, Mr. Henneguy was able to observe in the cells of 

 segmentation the very delicate phenomena lately pointed out by Auer- 

 bach, Blitschli, Strasburger, Hertwig, &c., and which accompany the 

 division of the nucleus, namely, the radiated disposition of the proto- 

 plasm at the two poles of the cell, the nuclear plate, the bundles of 

 filaments which start from it, and the other succeeding phases. 



This fact proves that the treatment undergone by the ovum does 

 not in any way alter the elements of the germ. 



To make cross sections of the germs and embryos thus extracted 

 from the ovum, they should be left for some days in Miiller's liquid, 

 and coloured with picro-carminate of ammonia. After having dehy- 

 drated them by treating them with alcohol of spec. grav. 0*828, and 

 then with absolute alcohol, they are put for twenty -four hours into 

 collodion. The embryo is then placed on a small plate of elder-pith 

 * ' Kevue Interuat. cles Sci.,' iii. (1879) 150. 



