642 APPENDIX. 



numerous that the whole body of the amoebae is filled 

 with them; they may be in a perfect state of preserva- 

 tion, or quite decolorized, or only recognizable by 

 their outline. The amoeba rarely contains leucocytes 

 or fat-globules. Various forms of bacteria are more 

 or less frequent inclusions, and black pigment gran- 

 ules and irregular brownish masses of pigment have 

 been noted by some observers. 



Biological Characters. The most striking and char- 

 acteristic feature of the amoeba is its motility. This 

 may consist either in an alteration of its shape or in 

 an actual change of place. Both of these phenomena 

 are produced through the mechanism of pseudopodia. 

 These latter are rounded, blunt, and homogeneous 

 processes formed by the more or less gradual protru- 

 sion of a portion of the ectoplasm at some part of the 

 periphery of the amoeba. The motion is sometimes 

 quite gradual and continuous, at others sudden and 

 jerky. The progressive movement that is, actual loco- 

 motion is brought about by the protrusion of pseudo- 

 podia, and into these, when they have reached a certain 

 size, the granular or vacuolated entoplasm, with its 

 other contents, flows with a more rapid movement 

 than that by which the pseudopodia themselves were 

 formed. Locomotion is generally observed to take 

 place in the direction of least resistance, a group of 

 cellular elements or some detritus being sufficient to 

 divert the course of the amoeba. The amoeboid move- 

 ments are also influenced by various factors, particu- 

 larly by variations of temperature. They are most 

 active at the mean temperature of the human body, 

 becoming less active as the temperature falls or rises 

 above this mean. They become motionless in a tern- 



