1916] Wilson: On tJie Life-History of a Soil Amoeba 245 



with five per cent acetic acid. Tlie last is entirely satisfactory. The 

 sublimate is always removed by washing in iodine alcohol. 



The stains used were blood stains such as Leishmau'.s, Wright's, 

 and Giemsa's; Rosenbusch's haematoxylin ; safJranin lichtgriin; 

 Mayer 's paraearmine ; Delafield 's haematoxylin ; Haidenhain 's iron 

 haematoxylin; Dobell's (1914) alcoholic iron haematin; and Alexeieff's 

 (1912 a) triple stain. Of these the last three have proved most satis- 

 factory. Dobell's stain is best for the cysts and for the division stages. 

 In addition to its efficiency it has the decided advantage of taking but 

 a short time for the whole process. Iron haematoxylin is good for the 

 flagellate stage, because the difi'erentiation may be carried further with 

 this than with Dobell's method without removing the stain from 

 the basal granule, though excellent preparations have been obtained 

 with the latter. Alexeieff's triple stain is good for staining the rhizo- 

 plast. In this method haematin was also used instead of liaematoxylin 

 and the preparations came out clearly. 



The counter-stains employed were erythrosin, eosiu, and orange G. 

 The intra-vitam stains tried were new methylene h\nc N, Janus 

 green, neutral red, Bismark brown, niblau, and niblau chlorohydrate, 

 but they were not successful in differentiating anything but cytoplasmic 

 granules. 



B. OBSERVATIONS 

 I. THE TROPHOZOITE 

 1. Movement 

 In the amoebas under observation here the body has one constant 

 character, namely that it progresses by means of one blunt, broadly 

 rounded or lobose, anterior pseudopodium. While the general direc- 

 tion of movement is in a straight line, there is not a constant flowing 

 direction forward, but rather outward from very near the anterior end 

 and alternating from one side to the other. ^A^len not in locomotion 

 the amoeba often alternately draws in and thrusts out a pseudopodium 

 on either side, advancing the one while withdrawing the other (pi. 18. 

 fig. fi"). This may take place at any point and may be repeated in- 

 definitely. The floating forms have from three to six blunt pseudo- 

 podia which may be long or .short. 



