Animal Evolution. 183 



mentation into quite a number of small globular 

 masses. The cyst then ruptures and the masses 

 escape as pyriform objects with the smaller end pro- 

 longed into a delicate filament, by which the young 

 spore propels itself in the water. Soon, however, 

 pseudopodia project from the entire surface of the 

 young spore, and the filament becomes confounded 

 with them. The cycle of life is completed by a 

 number of these modified spores assembling together 

 again, becoming completely fused (undoubtedly a 

 sexual process) and reconstituting a protomonas. 



The mycetozoon is a curious crawling fungoid animal 

 of naked protoplasm, spreading like a net-work of 

 egg yolk over old bark, tan, moss, leaves, etc. It has 

 affinities to both plants and animals, and is thus, as 

 many new forms constantly being discovered are, a 

 living cross between the two great organic kingdoms. 

 It foi ms Plasmodia which (mfuligo) encyst, and yield 

 millions of spores about T ^ 5U inch in diameter. 

 Two hundred species of mycetozoa have been de- 

 scribed. 



Although the amoeba resembles in its general char- 

 acteristics the lowest protozoa such as protamceba 

 and protogenes, it manifests a distinctly higher organi- 

 sation and predominates over them in permanence, size 

 attained, and physiological importance. It possesses 

 a clearly defined nucleus — usually a dark granular 

 concretion — and sometimes also a nucleolus, or nucleus 

 within the nucleus. The amoeba, in common with 

 nearly all protozoa, has a pulsating cavity called a 



