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CHARLES L. PARMENTER 
spermatogenesis from the early spermatogonia to the spermatids. 
He thus demonstrates that the conjugating elements are chro¬ 
mosomes and are morphologically identical with the spermat- 
ogonial ’chromosomes. That one of the homologues of each 
conjugated pair is maternal and the other paternal is very 
probable, as has been shown by the observations of Van Beneden 
(’83) and numerous later authors, especially Mulsow ( , 12). 
It remains to be seen whether the pairs of maternal and 
paternal homologues present in the germ cells during the matura¬ 
tion period maintain their identity in the germinal line between 
the time of fertilization and the first observations upon the sper¬ 
matogonia. This has been accomplished in part. Mulsow (T2) 
has followed the actual chromosomes of the living spermatozoon 
of a parasitic trematode, Ancyracanthus, into the egg, and has 
found the expected number of chromosomes in the two pro¬ 
nuclei and cleavage stages. He also observes that the chromo¬ 
somes of the cleavage nuclei show in many cases a tendency to 
lie parallel to one another, and suggests that this is an approxi¬ 
mation of maternal and paternal chromosomes. Boveri (’87, 
J 92) traced the chromosomes of the primordial germ cell of Ascaris 
univalens through the cleavages from the two-celled stage, 
and Moenkhaus (’04), Morris (T4), Richards (T7) have traced 
the persistence of individual chromosomes through several 
cleavages of hybrid eggs of Fundulus. If this persistence of the 
chromosomes is permanently maintained, the observations of the 
above authors make it probable that the maternal and paternal 
chromosomes form a duplicate series throughout the germinal 
line. 
b. Pairs in somatic cells. Since the existence of chromosome 
pairs can be considered to be all but proved throughout the 
germinal line, it remains to be seen whether or not the chromo¬ 
somes of the somatic cells, which are really descendants of those 
of the germinal line, still retain this duplicate series and thus give 
evidence of maintaining their individuality. 
The earliest observations bearing upon this question were 
made on Salamandra maculosa by Flemming (’82) and Rabl 
C85), who observed that the chromosome segments were not of 
