468 Prof. S. Apathy on 
upon the paucity of our supply of facts; it is, however, on 
the other hand merely a matter of arbitrary valuation : essen- 
tially it makes no difference whether an abyss, which we 
cannot cross, is ten metres or a hundred metres wide. A 
difference is a difference, and can really be neither greater nor 
smaller than any other. 
And wherefore must we exclude the Protozoa “ from 
Hiickel’s fundamental principle of biogenesis’? To what 
extent is our knowledge of the Protozoa to upset this principle ? 
For if there really are living creatures which are to be 
EXCLUDED from the fundamental principle of biogenesis, the 
latter is entirely invalidated. But has it recently been 
proved that we are confronted with insuperable difficulties if 
we assume that, in the case of the Protozoa also, ontogeny 
recapitulates phylogeny? It is true that the number of dis- 
tinguishable conditions of form through which the individual 
life of a unicellular animal passes is much smaller than that 
of the series of forms in its phylogeny must have been. Yet 
we see the same abbreviation—relatively still more—among 
the Metazoa also, and, just as in the Metazoa, the series of 
forms in the Protozoa often becomes somewhat more complete 
only in a cycle of several generations. In the same way 
larval adaptations and other coenogenetic conditions of form 
must play a perhaps even greater part among the Protozoa 
than they do in the case of the Metazoa. 
If phylogeny is really repeated in ontogeny it must be 
possible to rediscover in the individual development of a 
Protozoon THE INITIAL STAGE ALSO OF THE NON-NUCLEATE 
PROTOBLAST, THE STAGE OF THE MoNneRA. ‘The same 
demand must, however, be presented to the Metazoa also; for 
in their case, too, phylogeny cannot have proceeded from the 
nucleate Protoblast, but rather from the non-nucleate primary 
stage of all living forms. But the ontogeny of every Meta- 
zoon has hitherto appeared to commence with the stage of the 
egg-cell (or the reproductive cell in general), therefore with 
the nucleate Protoblast. Yet I now find it possible, owing 
to the discovery of the general diffusion of centrosomes 
(attraction-spheres) and their, so to speak, leading role in 
cell-divisicn, to trace back the ontogeny of the egg-cell also, 
and consequently that of all Protozoa, to the stage of the 
Monera. But the stage of the non-nucleate Protoblasts is 
at the present time always passed within the mother-cell, 
before delimitation of the daughter-cells occurs; for as soon as 
division has taken place in the centrosoma, the attracted area 
of which is equivalent to the unit of the Protoblast, therefore 
to its individuality, the parent individual has ceased to exist ; 
