172 Miscellaneous. 



spherical nucleus of an intense red colour and very distinctly 

 denned, the rest of the body remaining very pale. As the acetic 

 acid is very volatile, one has only to place at the edge of the covering- 

 glass a drop of glycerine, which penetrates and replaces the evapo- 

 rated acid, preserving the form of the zoospores. We thus obtain a 

 preparation which only requires luting to be rendered permanent. 



With the zoospores of (Edogonium, of which I had only a small 

 number, I followed a rather different method. I killed them by 

 exposing the drop of water for a minute to the vapours of osmic 

 acid of 1 per cent. ; I then cemented them under the covering-glass 

 by means of paraffin, coloured them with the picrocarminate, and 

 afterwards cleared them with the acetic acid and glycerine. Tho 

 action of the picrocarminate requires to be continued longer than in 

 tho method with alcohol. The nucleus, situated in tho middle of 

 the body, rather a little behind than in front, appears like a small 

 red sphere. 



These zoospores were killed during their period of mobility. The 

 nuclei could not be confounded with the amylaceous corpuscles 

 which are met with in many Volvocineae besides the true nucleus. 

 Tho amylaceous corpuscles never acquire a red colour in prepara- 

 tions made in accordance with the methods here employed. Wo 

 have therefore to do with true nuclei, combined with vibratile cilia 

 and with contractile vacuoles, in zoospores of Algae. The two Algae 

 shidied have zoospores belonging to two different types, those of 

 Microspora being flagellate, and those of (Edogonium. furnished with 

 a circlet of vibratile cilia. I am persuaded that if the zoospores of 

 the other Algae are suitably investigated a nucleus will be found in 

 in all of them. 



The new criterion proposed by Stein for distinguishing the two 

 organic kingdoms is therefore of no valuo. Moreover, to seek a 

 well-defined boundary between plants and animals seems to me to 

 be a search very little in harmony with all the recent progress of 

 biological studies. The latest works all tend more and more to de- 

 monstrate that all the barriers which it had been attempted to raise 

 between these two groups have nothing fundamental or real in 

 them. From the physiological point of view, Claude Bernard has 

 established incontestably the biological unity of the living world. 

 The same conclusion springs from all the morphological results that 

 we have attained. At present neither physiology nor morphology 

 furnish any exclusive character belonging to one or the other of the 

 two kingdoms. When we study the amphibiological creatures which 

 swarm in the lower grades of the living world we may therefore 

 sometimes be puzzled where to class them. It is necessary then to 

 consider the totality of the characters ; and, without having recourse 

 to a third kingdom, we may almost always siiccecd in finding in 

 them tendencies and affinities which enable us to assign them a place 

 in the existing categories. It is by the consideration of these 

 general characters that I am in complete accord with Cohn and other 

 writers in classing the Volvocineae among the Algae, side by side with 

 the Palraellaceae, the Conjugatae, and the Zoosporeae. — Comptes 

 Bendus, June 16, 1879, p. 1274. 



