290 FRANZ SCHRADER 
this same difficulty exists also in case of the bee where the dyads 
likewise seem to persist through the maturation. 
A few words might be said of the cytological work that Rosen- 
berg (17) has done on hybrids of the plant genus Hieracium. 
The maturation divisions are in most cases characterized by more 
or less irregularity. According to Rosenberg, a few of the un- 
paired chromosomes may undergo two equation divisions, while 
others are divided only once. But the very irregularity in the 
amount of pairing and the behavior of single chromosomes must 
make it practically impossible to be certain in these cases, except 
when none of the chromosomes are paired and the diploid number 
of chromosomes is found in each of the four resulting cells after 
two maturation divisions. Such a case, however, is not men- 
tioned by Rosenberg. 
Very puzzling conditions are met with in case of Dinophilus. 
Shearer (12) deseribed an entrance of the spermatozoa into 
the oogonia without a fusion of the nuclei. At one of the later 
divisions he assumed that the male nucleus did not divide with the 
female nucleus, so that the two daughter cells in one case have a 
biparental complement of chromatin, in the other a maternal 
only, the former becoming afemaleandthelatteramale. Nachts- 
heim (714), who recently investigated these conditions, finds 
that Shearer’s interpretations are erroneous to a large extent. 
Thus, there is no precocious entrance of spermatozoa into the 
oogonia, and unfertilized females may contain female-producing 
eggs. Instead of the peculiar phenomena described by Shearer, 
there is a fusion of oocytes, and the male and female eggs appar- 
ently differ only in the larger amount of yolk contained in the 
latter. Possibly the animal is a protandric hermaphrcdite and 
the number of oocyctes or nurse cells which join the ultimate 
germ cell determine whether the male or female state is evolved. 
How the chromosomal mechanism is correlated with this is by no 
means clear, especially since Nachtsheim and Shearer both con- 
cur in that maturation phenomena are apparently the same in 
both kinds of eggs (two polar bodies are given off and the diploid 
number of 20 is reduced to 10). Possibly here also the chro- 
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