CHROMIDIA AND THE BINUCLEARITY HYPOTHESES. 281 
not too firmly founded, and that a critical review of the facts 
does not justify all the inferences which have been drawn 
from them, 
My object therefore is to discuss first the facts, secondly 
the speculations based upon them ; endeavouring, by selecting 
the essential, to sacrifice detail for the sake of brevity. 
‘TERMINOLOGY. 
Before going any further I must define my terms. I shall 
use throughout only the two names introduced by Hertwig 
(02), namely, chromidia and chromidial net (Chro- 
midien, Chromidialnetz). Other terms are superfluous. By 
chromidia I understand any fragments of chromatin— 
irrespective of their shape or function—which lie freely in a 
cell,! without being massed together into a definite nucleus.” 
By chromidial net I understand any netlike arrange- 
ment of chromatin lying freely in the cytoplasm—regardless 
of its function. Both terms are purely morphological. It 
is sometimes convenient to speak of a whole system of chro- 
midia—considered as a unit—in the singular number, as a 
chromidium. 
Of other terms which have been used the following are the 
most important. Goldschmidt (04a) employs the terms 
chromidia in the wider sense, for all chromidial struc- 
tures of unknown function; chromidia (sensu stricto) 
for chromidia taking part in the vegetative functions of the 
cell; sporetia for chromidia which take part in forming 
gametes. This nomenclature has a physiological basis, 
and is difficult to use—except in a very few cases—owins- ‘to 
our present ignorance. Goldschmidt also introduced the: frm 
chromidial apparatus for any system of chromidia. |." 
eee . abe 
Mesnil (?05) uses a terminology which also has a pliysio- 
1 In the widest sense of the term. 14 
> With Schaudinn I believe the nucleus should be defined morpho- 
logically. The above definition is not intended to embrace chromatin 
particles of extraneous origin (e. g. ingested bodies). 
