196 BULLETIN: MUSEUM OF COMPARATIVE ZOOLOGY. 
the last spermatogonial division. Bigelow (:07, p. 371) is of the 
opinion “‘that a pairing of individual chromosomes does not occur at 
all in Gonionemus, but that synapsis occurs between the chromatic 
microsomes; and takes place while these are intimately associated 
in the homogeneous net” of the primary spermatocytes. A. und 
K. E. Schreiner (:06-07) in attempting to correlate the synapsis stage 
in all animals, have claimed that during the polar arrangement of the 
loops, at first present in the same number as the somatic chromosomes, 
a reduction in number to one-half takes place by a side to side conjuga- 
tion. This is apparently not true for many animals, where an end to 
end conjugation occurs. ‘The polar loops were not commonly observed 
in Tubularia, and their arrangement was not always clear. In some 
cases the number of loops was about half, in other cases more than 
half, the number of chromosomes in somatic cells. A reduction is thus 
suggested as taking place during this period, though the evidence is 
not sufficient to furnish convincing proof; and. no evidence could be 
obtained as to how the reduction occurred. 
Trinci (:07) found that after synapsis a continuous thread was 
present in Tiarella. This segmented into chromosomes,— though he 
does not say whether or not in a reduced number,— which anastomosed 
into a network persisting throughout the growth period. In Phialidi- 
um the chromosomes, formed in the same way, scatter through the 
nucleus and lose their staining capacity, but retain their individuality 
through the growth period. In Tubularia I find that the loops soon 
lose their polarity, and become more delicate and distinctly granular; 
in a few preparations threads lying side by side suggest a splitting of 
the loops, but the evidence on this latter point is so meager that it may 
be without significance. The chromatin in the germinative vesicle 
of eggs in later stages of growth is always finely granular and scattered 
along the reticulum, and all trace of the loops of the synapsis period is 
lost. 
The formation and behavior of the chromosomes in the maturation 
spindle I could not observe in Tubularia, and the important evidence 
which this would offer in regard to reduction is therefore lacking. 
It was possible, however, to observe these stages in Pennaria, and the 
conditions there may help to fill the gap in the history of Tubularia. 
In the equatorial plate of the first maturation spindle of Pennaria the 
chromosomes were present in the reduced number. Furthermore, 
they were partly in the form of tetrads, and in later stages in the form 
of x- and v-shaped figures; this suggests a splitting in the heterotypical 
fashion, such as is common in maturation mitoses. Since in the later 
4 
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