THE SPERMATOGENESIS OE LEPIDOSIREN PAKADOXA. 27 
The most important difference between the pre-meiotic and 
meiotic prophases is the entire absence in the former of any 
appearance of fusion of chromatin threads, such as takes 
place in zygonema. Although the spireme may often be 
observed to be longitudinally split (more often seen in the 
somatic than in the spermatogonal mitoses), I have never 
seen any suggestion of a fusion of definite widely separated 
threads. The really corresponding stages in the two periods 
seem to be (allowing for the different structures of the resting 
nuclei) the first resolution of the chromatin network of the 
spermatocyte into the leptotene threads, and the trans- 
formation of the chromatin blocks of the spermatogonia into 
the band-like chromosomes. 
The Reduction Question. 
While the majority of cytologists believe that the numerical 
reduction of the chromosomes is brought about by the 
syndesis or “conjugation ” of homologous chromosomes, con- 
siderable diversity of opinion exists as to how the syndesis 
takes place. Some students of heredity express the opinion 
that the mode of conjugation is inessential, the important 
point being the distribution of the chromosomes to the 
gametes in such a way that each gamete gets one member of 
each pair of homologous chromosomes. However, the dis- 
tribution in this manner depends upon their previous pairing, 
and this can only be established by observation. Now this 
cannot be said to have been done so long as different workers 
on the same group, or even on the same species, describe the 
syndesis as taking place at entirely different periods of the 
prophase, though each has observed and studied the stages 
described as conjugation by the others. 
The various schemes of “ conjugation ” which have been 
proposed can be roughly classified into two — metasyndesis 
and parasyndesis (Hacker). The latter term refers to the 
mode of conjugation upheld in this paper for Lepidosiren, 
and was originally proposed by von Winiwarter and developed 
especially by Gregoire and A. and K. E. Schreiner. Meta- 
