ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 1073 



of a mixture of 1 part glycerin and 2 parts 80 per cent, alcohol). 

 Both the quantity and the time are greater than is required for the 

 Cephalopods. For the isolation of the membrana limitans and the 

 recognition of the connection of the nerve-fibres and tbe retina cells 

 a strong action of the bleaching mixture is required. The sharpness 

 of the contours of the retina cells is said to be retained by mounting 

 the preparations in castor oil, and the isolation of the membrana 

 limitans is accelerated by transferring the bulb from the acid to weak 

 spirit (about 50 per cent.). By this treatment the vitreous body and 

 the lens swell up, while the membrana limitans remains unaffected. 



Preparing Spermatic Elements of Cockroach.* — Prof. v. la 

 Valette St. George recommends for the examination of the spermatic 

 elements of the small cockroach (Blatta germanica) a fluid which 

 unites the properties of not being harmful to cells, and that of staining 

 certain cell-parts deeply. This is iodized serum, rubbed in with 

 dahlia and filtered. The amniotic fluid can thus be replaced by 

 another indifferent fluid. Dilution of pure nuclear-staining media 

 with iodized serum did not give favourable results. For fixing the 

 tissues the author used the mixtures recommended by Gilson and 

 Carnoy, and with the same result, and also Flemming's fluid. 



Preparing Accelous Rhabdoccela.j — M. Y. Delage, as reported 

 ante, p. 790, has demonstrated the presence of a distinct nervous 

 system in accelous Bhabdocoela, the absence of which has hitherto 

 been considered as characteristic. His methods are as follows : — 



1. Staining with gold chloride, (a) Examination of the whole 

 animal. Fresh Convoluta are placed in a watchglass filled with sea- 

 water. The greater part of the latter is removed and replaced by one- 

 third formic acid. After two minutes the formic acid is displaced by 

 a copious quantity of a 1 per cent, solution of gold chloride acting 

 for 10 to 12 minutes. From the gold solution the Convoluta are 

 transferred to a 2 per cent, solution of formic acid in which they 

 remain in the dark for one to three days. The progress of the 

 reduction of the gold must be watched. The author considers it to 

 be advantageous to allow the staining to proceed to complete violet 

 or even non-transparency and to decolorize slowly by means of a 

 1/2 per cent, solution of cyanide of potash (2 to 24 hours). The 

 effect of the last reagent is interrupted by a 2 per cent, solution of 

 formic acid. By this treatment all the tissues are stained violet, the 

 nervous system first, as it is the last to be decolorized. Mount in 

 glycerin or balsam. 



(b) If the author intended to cut the animals, he crushed them 

 gently on a slide and allowed some one-third formic acid to run under 

 the cover-glass. This altered the form of the Convoluta as little as 

 possible and kept them extended. Further treatment was as above. 

 From the 2 per cent, formic acid, the author passed them into 60 or 



* Arch. f. Mikr. Anat., xxvii. (1886) pp. 1-12 (2 pis.). See this Journal, 

 ante, p. 590. 



t Arch. Zool. Expe'r. et Gen., iv. (188G) pp. 109-GO (2 pis.). Cf. Zeitschr. f. 

 Wiss. Mikr., iii. (1886) pp. 239-41, and this Journal, ante, p. 796. 



Ser. 2.— Vol. VI. 4 A 



