1880.] 



MICKOSCOEICAL JOURNAL. 



37 



Slides ;" " How to Cultivate Fresh- 

 water Algae in Aquaria;" "Notes 

 on Actinosphwrium eichornii; " be- 

 sides others which are promised. 

 Judging from the present outlook, 

 it will be a long time before this 

 Journal becomes a mere reprint of 

 articles selected from other perio- 

 dicals. 



REYIEW. 



In Zoologischer Anzeiger the fol- 

 lowing brief notice is published by 

 Dr. W. Haacke, which we translate 

 quite literally : In a work soon to 

 appear " On the Blastology of the 

 Genus Hydra," it will be shown 

 that until now only two not green 

 hydra species have been distinguish- 

 ed with certainty. 



In the first, which I call H. 

 Tremhleyi, the tantacles of the buds 

 appear together at the same time ; 

 in the other, which I call //. 

 Roeselii^ only two opposite tentacles 

 appear on the buds at first, the suc- 

 ceeding ones are produced singly. 



The third and last species to be 

 certainly distinguished, hitherto 

 the only such a one of the genus 

 Hydra remains II. viridis. 



In the above-mentioned work I 

 vdW give particulars of my discov- 

 eries concerning the special rela- 

 tions in the development of the 

 tentacles on the buds of H. Hoeselii, 

 which are of great interest, and 

 also about their great morphologi- 

 cal signification. 



In Science Gossip we find an 

 article on " How to Stain Vegeta- 

 ble Tissues," which seems to em- 

 brace so much that is practical, that 

 we condense the directions as fol- 

 lows : 



All anilin dyes are more or less 

 fugitive when applied to vegeta- 

 ble tissues, so that in order to make 



a double-staining two dyes of dif- 

 ferent colors must be used, one very 

 fugitive while the other is much 

 less so. " If any vegetable section 

 containing hard and soft tissue be 

 dyed in such colors, either together 

 or separately, and afterwards washed 

 to a certain extent, it" will be found 

 that the more fugitive dye still 

 lingers in the harder tissue, which 

 gives it up less readily than the 

 softer parts ; these latter still retain- 

 ing the permanent dye, which is 

 usually not so penetrating as the 

 other dye, and is therefore over- 

 powered by the same in the harder 

 tissue." We have never seen a 

 clearer exposition of the principles 

 which govern the selection of color 

 in double-staining vegetable tissues. 

 It may not be strictly accurate, and 

 the well-known fact that the selec- 

 tion of color in the tissues is not 

 always the same, when they are 

 treated by different processes, may 

 not be in its favor ; but there is 

 no doubt that by keeping the above 

 explanation in mind the manipula- 

 tions will be conducted more intel- 

 ligently and consequently with bet- 

 ter success. 



The secret of double-staining 

 with anilin colors lies, therefore, 

 in the partial washing out of the 

 first or most fugitive color. To 

 cease washing at the right moment 

 requires judgment and experience. 

 The writer of the article referred 

 to uses carmine, which is a per- 

 fectly " fast " dye, instead of an 

 anilin color, and in this way over- 

 comes one difficulty ; for the other 

 color he uses the anilin green 

 known as " iodine-green." 



The solution of carmine is made 

 by dissolving 10 grains of number 

 40 carmine in 10-15 grains of strong 

 anmionia aiding the solution by a 

 gentle heat, then adding 200 grains 

 of distilled water and filtering. 

 For ordinary use dilute this solution 



