306 J. E. S. MOORE. 
genesis in a great variety of animal forms. Now, exactly simi- 
lar figures are obtained before the division of the pollen 
mother-cells, during the formation of the so-called “ para- 
nucleus” in plants; but considerable diversity of opinion 
exists on the botanical side as to the real or artificial nature of 
the paranucleus and its associated contraction figure, 1. e. 
whether the whole appearance is not in reality more a ‘‘Gerin- 
nung’s Erscheinung” than a reality. However this may be, 
I do not believe that the one-sided nuclear figures seen at a 
corresponding period in the spermato- and ovo-genesis of 
animals, and with which most histologists must be quite 
familiar, are artifacts at all; and whether the contraction 
really exists in plants or not, it has been generally conceded 
by the botanists I have interrogated on the subject, that it is 
especially related to the time in question, while Professor 
Farmer tells me that such shrunken nuclear figures are practi- 
cally diagnostic of the synapsis in certain liverworts of Ceylon, 
and so there can be little doubt that there exists, at any rate at 
this period, a peculiarly sensitive condition of the chromatin, 
common to both animal and plants. 
55. In Elasmobranchs, Mammals, Amphibia, and probably 
many other animals, the division which immediately follows 
the synapsis is, as will be seen from §§ 23—387, different 
from all those preceding it. The chromosomes as_ they 
emerge from the reticulum of rest, being no longer longitudi- 
nally-split rods, but closed loops or rings, the divisions thus fall 
under the category of Fleming’s heterotype. In animals the 
exact form and placing of these closed loops differs a good deal 
in different forms, but they all agree in this, that the loops 
split finally in the equatorial plane. In Elasmobranchs, 
Amphibia, and many other forms, the loops at first become bent 
up in the equatorial region of the spindle, so that when seen 
in profile they present the appearance of two Greek omegas 
placed side by side, the ends of which unite towards the poles 
(Diagram IV, 1,4, c). The outer curves and the closed ends 
of these figures are much thickened, and consequently the space 
between the two enclosed omegas is reduced to a mere slit. 
