PROGENITORS OF MAN. 279 
proof of the earlier existence of this most ancient ancestral 
stage, based upon the fundamental law of biogeny, is pos- 
sibly still furnished by the circumstance that, according 
to the assertions of many investigators, in the beginning 
of the development of the egg, the cell-kernel, or nucleus, 
disappears, and the egg-cell thus relapses to the lower stage 
of the cytod (Monerula, p. 124; relapse of the nucleated 
plastid into a non-nucleated condition). The assumption 
of this first stage is necessary for most important general 
reasons, 
SECOND STAGE: Amebe, 
The second ancestral stage of Man, as of all the higher 
animals and plants, is formed by a simple cell, that is, a little 
piece of protoplasm enclosing a kernel. There still exist 
large numbers of similar “ single-celled organisms.” Among 
them the common, simple Amcebee (vol. i. p. 188, Fig. 2) 
cannot have been essentially different from these progenitors. 
The form value of every Amceba is essentially the same as 
that still possessed by the egg of Man, and by the egg of 
all other animals. (Vol. i. p. 189, Fig. 3.) The naked egg- 
cells of Sponges, which creep about exactly like Amcebe, 
_ cannot be distinguished from them. The egg-cell of Man, 
which like that of most other animals is surrounded by a 
membrane, resembles an enclosed Amceba. The first single- 
celled animals of this kind arose out of Monera by the 
differentiation of the inner kernel and the external proto- 
plasm; they lived in the earlier Primordial period. An 
irrefutable proof that such single-celled primeval animals 
really existed as the direct ancestors of Man, is furnished. 
according to the fundamental law of biogeny (vol. 1. p. 309) 
