432 



Mr. T. Goodey. The Excystation of [Feb. 28, 



Methyl green, saturated aqueous solution + 1 per cent, acetic acid : 

 membranes not stained, contents of endocyst immediately stained. 

 Iodine green : same result as with methyl green. 



Safranin, strong aqueous solution : membranes not stained, cyst contents 

 freely stained. 



Gentian violet, strong aqueous solution : membrane not stained, cyst 

 contents stained. 



Eosin, strong aqueous solution : membranes not stained, cyst contents 

 stained. 



Carbol fucbsin, the strong bacteria stain : membranes not stained, contents 

 of endocyst stained deep red. 



Haematoxylin (Heidenhain's) : film-preparations made by hatching out 

 Colpoda in 1-per-cent. hay-infusion + egg white and killing the excysting forms 

 with osmic vapour, were stained with iron haematoxylin. The ectocysts 

 stained dark blue or purple ; the endocysts stained the same tint but not so 

 intensely. Haematoxylin (Delafield's) : in films prepared as for Heidenhain's, 

 but stained with this preparation, the ectocysts stained purple, the endocysts 

 a pale reddish or bluish purple. From these records it will be seen that only 

 the haematoxylin stains touch the cyst-membranes. This is interesting, for 

 Fabre considered that many aniline stains affected the cyst-membranes 

 of ciliates. 



The Nature of the Process of Esxystation. — Butschli* says that little is known 

 on the manner in which the cyst-contents are reorganised prior to excystation. 

 jSTo doubt water penetrates into the interior causing the organism to swell up 

 and the contractile vacuole to begin pulsating. The cilia reorganise them- 

 selves, but how they do so is not accurately known. The imbibition of water 

 doubtless plays an important part in the rupturing of the ectocyst. 



He also suggests that instead of Colpoda escaping from the temporary 

 division-cysts through the narrow aperture, they may perhaps have the power 

 of dissolving the membrane in a particular place. 



Many observers have recorded the fact that the ectocyst is caused to 

 rupture, as Butschli suggests, by the increased volume of the cyst contents 

 owing to the imbibition of water. The exact manner, however, in which 

 the organism manages to get out of the endocyst does not appear to have been 

 determined. It is on this interesting point that the present investigation 

 throws light. 



In carefully watching the movements of Colpoda within the transparent 

 endocyst, it is noticed that the organism rotates freely and that the endocyst 

 gradually increases in diameter ; the wall becomes thinner and thinner until, 

 * Butschli, O., ' Bronn's Klassen des Thierreichs,' " Protozoa," Abt. Ill, p. 1664. 



