752 
Digby .— The Somatic , Premeiotic , 
Another subject of discussion amongst cytologists is the question as tc 
the origin of the univalent chromosomes which make up each bivalent paii 
in the heterotype prophases. One school contends that the chromosome' 
are arranged side by side in the spireme (11) (1910), the other that they art 
joined end to end ( 4 ) (1905). 
In Gciltonia the univalent chromosomes finally arise by a splitting 
apart of the thick bivalent segments, but these bivalent segments are 
composed of two primary distinct lengths of univalent spireme which con¬ 
ceivably may have joined during synapsis, although there is no direcl 
evidence of this, but certainly become definitely approximated during the 
hollow-spireme and second-contraction stages. 
As there is so much variety in the spireme as it comes out of synapsis 
a variety apparent both in the thickness and in the arrangement of its loop' 
and strands, and as the presence of anastomosis certifies that the arrangement 
and pairing of the homologous chromosomes cannot yet be in order, it seems 
possible that as long as the homologous chromosomes do pair eventually 
it does not signify when they pair or in what manner they are joined. The 
important point which Galtonia demonstrates is that its spireme is univalent 
Whether these univalent strands join with their homologous pairs telo- 
synaptically or parasynaptically, or by any other intermediate method 
between these two extremes, resolves itself merely into a question oi 
non-essential detail. 
Lastly, the varied character and the great inequality shown by the 
nuclei of Galtonia throughout all the division figures must once more be 
emphasized. There is no 4 cut and dried ’ definite arrangement; it cannot 
possibly be stated a priori that the formation of each individual chromosome is 
arrived at by some one particular method. The elaborations and intricacies 
are endless, and all that can be said is that the course of events appear to 
trend in some one direction, and that finally the same goal is reached, though 
the method actually pursued may be subject to great variation. 
Summary. 
1. The chromosomes in the somatic and premeiotic divisions are 
formed from the telophase of the preceding division by an alveolization oi 
the chromosomes and partial separation of the two sides, followed b^ 
a reconcentration of the same. 
2. The parallel threads and portions of linin present in the early hetero¬ 
type prophases are homologous with those in the somatic and premeiotic 
prophases. They are the remains of the alveolized portions of the chromo¬ 
somes of the telophase of the last premeiotic division. There is no rest 
between the premeiotic and meiotic divisions. It is believed that during 
synapsis the parallelisms concentrate to form whole, or portions of whole 
somatic chromosomes. The spireme as it comes out of synapsis is 
