278 
Sidney 1. Kornhauser 
seems to be previous to syndesis no polar arrangement of the threads 
followed by a gradual parallel union progressing from tlie positive pole. 
Instead, leptotene thi'eads, parallel or partially united in pairs, cross 
one another m an irregulär fasliion. Gerard has described the fonnation 
of a double spirem not by Splitting, but by the apposition of the gra- 
nules from a network into two long tortuous filaments lying side by side 
and later segmenting. 
The cases of parasynapsis described in insects are irreconcilable with 
the vievs of those who maintain that there is first a polar arrangement 
of the threads united end to end in pairs (metasyndetically), and that 
this is followed by a gradual broadening and Splitting of the granules 
(Davis ’08; Büchner ’09). In Enchenopa it was found that doubling 
took place before the bouquet stage, that no gradual broadening of the 
leptotene threads could be discerned, and that the chromatic granules 
of the double threads in the early zygonema were not symmetrically 
placed on the two sides of the light longitudinal line of union. 
Montgomery (’OO, ’Ol, ’03, ’04) maintained that the chromosomes 
paii’ed end to end, although he suggested (’Ol, p. 225) that the bivalent 
chromosomes of vertebrates might be formed by two univalent chronioso- 
mes becoming apposed to each other along their whole length, and that 
a subsequent opening out of the chromosomes along the line of union, 
the ends remaining connected, might thus form the ring-shaped chromo- 
somes of heterotypic divisions (amphibians, annelids, and insects). This 
method of conjugation of the chi'oniosomes (parasyndesis), he finally 
described for the hemipteron EmcMsius, and he also convinced himself 
(’ll, p. 754) of the reality of parasyndesis in the amphibian Plethodon. 
The ring-shaped bivalents of the prophase of Euscliistus originated, not 
by a secondary approximation of the ends of two chromosomes previously 
joined end to end into U-form bivalents, but from the persistence of 
the Connections at their ends of two chromosomes which had been parallel 
along their whole length. This has also been found to be true for the 
ring-shaped bivalents of Enchenopa (Figs. 103—117, Plate XX) and Äm- 
phiscepa (Figs. B— H). The latter often retained the double connection 
in the first maturation division. In Euschistus, as in Enchenopa, the 
rings do not persist, but straighten out before the spindle is formed. 
Recently, Stevens (’12a) has described parasyndesis for the ortho- 
pteran Ceuthophilus. The method of chromosomal union which she has 
described is not merely a parallel apposition of two leptotene threads, 
but, in addition, a twisting of the two about each other. It is here, per- 
liaps, that suitable material for a consideration of Janssens’ “chiasmatype” 
