1913.] 



Colpoda cucullus from its Resting Cysts. 



437 



used. The object of the experiment was to obtain a colour reaction for the 

 presence of a carbohydrate in the culture-liquid containing the products of 

 the digestion of the endocysts by the enzyme secreted by the Colpoda. 



The cultures were made in the hollows of cavity slides, and the cysts of 

 the large variety of Colpoda cucullus were used. After a large number 

 of organisms had become active, the cultures were unsealed, and the liquid 

 was taken up in a capillary pipette and transferred to a small glass tube. 

 This liquid was practically free from ectocyst membranes, though it is 

 possible there may have been a few present, for it was impossible to examine 

 the liquid under the microscope. There may also have been one or two fine 

 threads of cellulose present from the filter paper on which the cysts had been 

 collected from the original culture of Colpoda. 



To the liquid was added an equal volume of strong hydrochloric acid, and 

 the mixture was boiled for half an hour on the water-bath, in order to 

 hydrolyse any maltose present to dextrose. A little scatole was added and a 

 drop or two more of strong hydrochloric acid. On gently heating this 

 mixture over the Bunsen flame a pale purple coloration resulted, indicating 

 the presence of a carbohydrate in the liquid. 



On heating up some of the original culture-liquid, i.e. distilled water 

 containing O'Ol per cent, caustic soda, with strong hydrochloric acid and 

 scatole, no coloration was obtained, nor was any coloration produced when 

 distilled water alone was tested in this way. The liquid, then, which had 

 been used for the excystation of Colpoda clearly contained a carbohydrate. 

 That the carbohydrate was there as a product of the digestion of the endocyst 

 of Colpoda cannot be definitely asserted, since there may have been present 

 in the liquid a trace of cellulose, or ectocyst membrane. Whether this 

 supposed cellulose and ectocyst would be sufficient to account for the colora- 

 tion produced cannot be stated, but I consider it negligible, and think it 

 does not vitiate the result of the test. 



No special emphasis, however, is laid on this test as an indication of the 

 carbohydrate character of the endocyst. The fact that it is digested by 

 diastase and fails to show any reactions to protein and other tests is sufficient 

 to show that it is a true carbohydrate. 



Note on the Endocyst of Gastrostyla steinii. 



A few cultures were made with the resting cysts of Gastrostyla steinii, and 

 several active organisms were found after three hours' incubation at 30° C. 

 There appear to be ectocysts and endocysts in the resting cysts of this 

 organism as in Colpoda. 



The process of excystation is slower than in Colpoda cucullus, and many 



