74 ATLAS OF BIOLOGY. 



XII. A period in the ingestive phase. 



The animal was observed to move round the glassy fragment figured *, for a period of 

 twenty minutes, finally rejecting it in favour of the small vegetable organism, f.p. ; in all 

 probability, any nutritive matter which may have been adherent to it was meanwhile 

 taken up. 



XIII. A portion of Fig. XII., after the organism,/.^., had been ingested. 



XIV. AND XV. Successive stages in the assimilative and excretive processes ; XV. 

 was drawn 19 20 hours later than Fig. XIII. The digestible parts of the ingested 

 organism were assimilated by the Amoeba, and the refuse ejected, as figured, in a distorted 

 disintegrating condition.* 



The contractile vacuole. c.v., is drawn in Fig. XV., at both systole and diastole. 



Engelmann (103) has made some observations upon the physiology of this organ. 



XVI., XVII., XVIII. Successive stages observed in the reproductive process of the 

 same organism, two days later. XVI. represents the nuclear-division stage, and the two 

 remaining figures are phases in the division of the cell. 



The organism figured above was a small Amoeba having a conspicuous nucleus, found 

 in the sediment from a small fresh-water aquarium. Its probable specific identity is 

 left an open question, and the observations of Wallich (125) show how far such a determina- 

 tion might be reliable upon purely external appearances. 



Gruber (107 to 110) has recently entered upon investigations of the greatest value, 

 concerning both this subject and the behaviour of the nucleus among unicellular 

 animals. 



FIG. XIX. A similar organism, encysted. 



Three or four hours later the cyst disintegrated, liberating the animal. 

 (Figs. XI. to XIX. all drawn under Zeiss. D. 3.) 



The Protococcus. 



Figs. XX. to XXII. represent successive stages observed in the life-history of 

 Protococci, scraped from the bark of a tree. 



A somewhat similar difficulty arises here as with Amoeba, with reference to the specific 

 identity. The latest paper on the subject is that of Klebs (114). 



XX. A group of organisms in the dried state. 



The three stages in division figured, were observed in one individual. 



- The appearances presented were such as to presuppose a digestive action on cellulose. 



