n 
W. E. AGAR. 
extended, I might add as the most recent examples, Planaria 
(Arnold), Dicrocoelium (Dingier). 
One of the objections which Meves (1907) urges against 
interpreting what takes place in the zygotene stage as a 
fusion of originally separated threads, is that the linin bridges 
which connect up all the threads (not merely the members of 
the conjugating pairs) must prevent the necessary movements. 
In Lepidosiren, however, it is a matter of observation to 
determine that threads, at one time separate, do move 
together and fuse in spite of the existence of linin bridges. 
Whether we must suppose that the linin connections are 
sufficiently elastic to allow of the necessary movement, or 
whether Gregoire is right in supposing that the approximation 
of the threads is accompanied by a breaking of the connections, 
which may be formed again afterwards, is a point which must 
be left undecided so far as Lepi do siren is concerned, though 
the former view seems to be indicated. 
Following immediately after the bouquet is the strepsitene 
or diplotene stage, in which the conjugavits which were 
temporaril} 7 united in the pachytene loops separate again. 
In Lepidosiren this stage is complicated by the fact that a 
very pronounced synizesis (synapsis of some authors) now sets 
in. As it is now certain that synizesis does not always coincide 
with syndesis (it does not for instance in Lepidosiren) 
the discussion as to whether the contraction is or is not an 
artefact has lost the interest which it had when it was 
supposed by many workers to be the necessary concomitant 
of the conjugation of the chromosomes. In my material it 
always occurs between the bouquet stage and the appearance 
of the definite chromosomes, both in testes fixed with 
Flemming and with corrosive-acetic, and equally in all parts 
of the section. The stage in which it occurs is therefore that 
in which the individual members of the tangled mass of 
chromatin threads undergo a very pronounced contraction, 
and it seems that this fact must set up a condition of stress 
within the nucleus, the visible result of which is the clumping 
together of the threads at the side of the nucleus away from 
