286 RECORD OF CURRENT RESEARCHES RELATING TO 



Certes has now experimented with the view of ascertaining whether 

 this general law extends to the Infusoria, Bernard showed that 

 glycogen is revealed under the Microscope " by the wine - red, 

 purplish, or mahogany-red colour which it takes under the influence 

 of iodine,* and Kanvier, by means of iodized serum, proved its 

 presence in the lymphatic cells, which, in more than one respect, 

 may be compared to Amoehce. " The mahogany-brown colouring by- 

 iodine," he writes,! " is the characteristic reaction of glycogen. , . . 

 It is homogeneous ; exists in a kind of gummy condition which 

 enables it to spread everywhere ; it may even escape from the cell 

 and form little drops. If the action of the iodized serum is pro- 

 longed these little drops coalesce and end by producing round the 

 cell a border of a brown colour. These characters added to the iodine 

 colouring are common to glycogenic matter wherever it is found." 



Treated with iodized serum the greater part of the Infusoria are 

 not diffluent. It is hence possible to follow the phenomena caused 

 by iodine and to prove that they in no wise differ from those 

 described by Eanvier. At the outset, the mahogany-brown colour 

 appears diffused ; but if the action of the reagent is regulated, and if 

 the Infusoria are gently compressed, the colour is seen always to 

 spare certain organs ; sometimes even it shows a sort of localization. 

 The nuclei, the nucleoli, and the contractile vesicles are never 

 coloured. The same is the case with the cuticle, the vibratile cilia, 

 the contractile filament of the Vorticellce ; and even, when they exist, 

 with the gastric vacuoles. The sarcodic expansions of freshly killed 

 Infusoria, on the contrary, become mahogany or wine-red colour, and 

 the colloid matter, in contact with water, slowly diffuses through it. 



According to M. Certes' observations, the glycogenic function 

 would be independent of the chlorophyllic function, even in the case 

 of flagellate Infusoria which are very sensitive to light, and 

 in which the chlorophyll certainly plays an important physio- 

 logical part. In Euglena acus, the grains of chlorophyll are more or 

 less blackened and the nucleus stands out clearly, whilst the rods 

 of Paramylon, also colourless, appear in a matrix of mahogany- 

 brown protoplasm. 



In the Amoehce and Rhizopoda the glycogenic reaction is less 

 constant than in the Infusoria. When it is produced, the nucleus 

 and the contractile vacuole are never coloured. 



The author has not observed that the Infusoria which are conju- 

 gating, or are in process of reproduction by fission, are much more 

 deeply coloured than the others, and has not hitherto succeeded in 

 sensibly modifying the glycogenic function by varying the conditions 

 of temperature and the nutritive media. The vitality of the animals 

 is, on the contrary, an important factor. Infusoria which are crushed 

 or killed by reagents no longer become coloured. Nevertheless, if 

 they have been killed by desiccation, a certain number are always 

 found containing a quantity of glycogenic matter. 



The author finally points out briefly the effect of iodized serum on 



* Loc. cit., ii. p. 91. 



t ' Traite technique d'Histologie,' p. 158. 



