Beer. — Studies in Spore Development . II. 7 1 1 
behaviour of the spiremes of different plants. In some, such as the lily, 
the longitudinal separation of the spireme into two halves is a conspicuous 
and unmistakable phenomenon, whilst in others, such as several species of 
Oenothera and in many (or possibly all) Compositae, this division is either 
entirely wanting at this stage or the two halves remain so closely pressed 
together that it is most difficult to demonstrate them. 
In any case, whether the spireme of the Compositae obscurely divides 
longitudinally or not, the facts offer very little support to those who believe 
in the existence of two independent spiremes which are supposed to approach 
one another and to become closely approximated. No chromatin bodies 
(gamosomes) and no threads can be seen approaching one another in order 
to become intimately associated. 
A fine reticulum, without prochromosomes or any other such definite 
chromatic aggregates upon it, passes into synapsis ; here the reticulum 
becomes transformed into a spireme which is, at first, very delicate, but 
which gradually thickens and becomes shorter. No definite parallelism of 
the filaments can be seen other than is inevitably connected with any dense 
coil of thread. The close synaptic coil gradually unfolds and passes into 
the hollow spireme, but never once do we find parallel threads coming 
together to meet laterally in order to become intimately approximated. 
This spireme has every appearance of being undivided, but should it 
prove to be longitudinally split there can be no doubt that the two halves 
are so closely merged together from the first that no other explanation is 
possible, but that they have arisen from the real longitudinal division of 
a previously single thread. 
As will be seen below, the later stages of the second contraction often 
simulate the appearance of a longitudinally divided spireme when the long 
loops, with closely approximated sides, are viewed in thin sections. It is 
conceivable that some confusion between the two stages has taken place in 
the past and that some of the illustrations of a split spireme may more 
correctly be referred to the later stage. 
Second Contraction. 
During the next stage in the history of the nucleus the hollow spireme 
again draws itself together to form the so-called ‘ second contraction which 
has been met with by many observers of the reduction phenomena. The 
interpretation which has been placed upon this condition of the nucleus is, 
however, very contradictory. 
Some writers, such as Farmer and Moore (5), Mottier (18), Lewis (14), 
Miss Digby (4), and Dr. Fraser (7, 8), regard this stage as an important one 
in the development of the bivalent chromosomes. 
Other cytologists, however, amongst whom are Rosenberg (19, 20) and 
