SPERMATOGENESIS OF EUSCHISTUS 753 
von Winiwarter; amphiténe, Janssens); the univalents then 
approximate so closely as to form thick double threads, the 
pachytene condition (von Winiwarter; pachynema or spirem, 
Grégoire) ; then each such thick thread becomes distinctly double 
again by a process of unrolling of the constituent univalents 
(diploténe, von Winiwarter; strepsitene. Dixon; strepsinema, 
Grégoire). At any period of these stages a contraction of the 
chromosomes may take place (synapsis, Moore; synizesis, 
McClung). Thus just before and after the pachytene condition 
each geminus may show a split along its length, which is the path 
of approach and retreat of the univalents and not a longitudinal 
split of univalents; a true longitudinal splitting of univalents 
does not occur until late in the diakinesis or may not appear until 
the anaphase of the reduction division. 
The other chief view of the conjugation of the chromosomes 
was introduced by me, also in 1900, and is that termed by me 
end-to-end conjugation and by Hacker metasyndesis (telosy- 
napsis, Wilson). I interpreted the phenomena in this sense first 
for Peripatus, later also for Euschistus, Plethodon, Syrbula and 
Lycosa. It maintains that shortly after the last spermatogonial 
mitosis the chromosomes conjugate end to end, or, in the case of 
ring-shaped ones, by both ends, and that subsequently (my postsy- 
napsis stage, equivalent to the diplotene) each univalent element 
becomes longitudinally split. This view gives no satisfactory 
explanation of the pachytene condition. 
The observations of the present paper are in accord with the 
view IID, which implies parasyndesis with prereduction. My 
original conclusion was right that in the species examined by me 
the chromosomes are paired end to end in the first maturation 
spindle and in the late prophase, whereas in most other cases they 
' lie in these stages in parallel juxtaposition. But I made my 
error, as Grégoire has pointed out, in overlooking or giving scant 
attention to most of the stages preceding the pachytene condition, 
which are necessarily the decisive ones; I also employed too low 
powers of magnification for such delicate determinations. During 
the past year I have also convinced myself of the occurrence of 
