CHROMIDIA AND THE BINUCLEARITY HYPOTHESES. 315 
This encasement hypothesis is, in face of the facts, to my 
mind exceedingly far fetched: and moreover, were it true, 
would not shed any light on the fundamental problem 
involved. For it is obvious that by assuming the original 
presence of a separate kinetic nucleus—ancestor of the centro- 
some—in the cell, we have merely put the problem a little 
further out of reach. What gives the kinetic nucleus itself 
the ability to divide? Its centriole? ‘Then is the centriole 
another kinetic nucleus within the kinetonucleus ? And has 
its own kinetonucleus again inside that, and so on, in an 
unending box-within-box system? One is forcibly reminded 
of the ‘ scatulation theory” of the preformationists. 
TexT-FIG. 25. 
Sections through the nucleus of Huglena: a, resting; b, in 
division; C, the so-called ‘“nucleolocentrosome.” (After 
Keuten, °95.) 
It is curious to note how a structure like the nucleolo- 
centrosome of Euglena can be regarded on the one hand 
(Goldschmidt, Popoff) as a chromidial apparatus, and on the 
other (Hartmann, Prowazek) as an actual independent, 
encased nucleus (text-fig. 25). 
There can be little doubt that the karyosome is really a 
structure of physiological significance in many cases, and, as 
such, a structure which cannot be homologized throughout 
the Protozoa. This has been very clearly brought out by 
Siedlecki (’05) in his admirable study of the coccidian Caryo- 
tropha. The karyosome, he maintains, is “an amplification 
of the whole nuclear apparatus.” For him, ‘we have in a 
