THE SPERMATOGENESIS OF LEPIDOSIREN PARADOXA. 37 
with this the first maturation division is omitted, and 
consequently each egg gets the somatic number of chromo- 
somes. Should this be the case, it emphasises strongly the 
double function of the conjugation of the chromosomes. 
If Strasburger is right in interpreting the absence of a synaptic 
contraction in Elatostema sessile and Wikstroemiaas 
indicating an absence of chromosome conjugation it shows of 
course that its periodical occurrence is noc essential to every 
form, but this does not destroy its significance any more than 
the occurrence of a few parthenogenetic species does away 
with all the meaning of conjugation of gametes. 
Pairing of Chromosomes outside the Meiotic Period. 
In somatic and spermatogonial equatorial plates it can be 
seen at first glance that the arrangement of chromosomes is 
not haphazard. This was noticed by Murray in his paper on 
the somatic mitoses in Lepidosiren (in various embryonic 
tissues). He says: l( Die Grossenunterschiede der Chromo- 
some n kommen aucli in anderen Weise zum A usd ruck, iudem 
sie die Anorduung der Kernelemente in der Tochterplatte zu 
bedingen scheinen. In der Mitte . . . liegen die 
kleinsten Chromosomen . . . Die grossten Elemente 
liegen ganz peripher . . . Die Mittelgrossen chromosomen 
nehiuen eine Zwischenstellung ein.” 
These observations of Murray’s I can fully confirm and 
extend them to the spermatogonial mitoses. In the metaphase 
of both somatic and spermatogonial divisions the chromosomes 
are generally arranged in a hollow ring, so that the small 
chromosomes are not situated to the inside of the larger ones, 
but we find the latter grouped towards one side and the 
former towards the other side of the equatorial plate (PI. 1, 
fig. 6). In the anaphase the ring shape is destroyed and the 
distribution described by Murray appears (PJ. 1, fig. 7). 
In the large spermatogonia the exact delimitations of the 
chromosomes are not always easy to determine owing to their 
great length, which causes them to overlap one another 
