The Development of the Spores of Equisetum. 263 
the pairs of chromosomes which subsequently develop. I think 
there can be no doubt that the pairs of parallel chromosomes which 
can be quite clearly seen in the later stages of the prophase and 
during the metaphase are derived from the segmentation of a 
spirem which consists of two parallel halves. 
The very important point, however, still remains to be determined, 
whether the two parallel halves of the spirem are derived from the 
splitting of an originally single thread or by the approximation of 
two separate and distinct threads. 
In the light of what has been observed in other plants in which 
the chromosomes have been seen to originate from a double spirem, 
and from certain, as yet not very conclusive, indications in Equisetum 
itself, we may expect the latter alternative to prove the correct one, 
although it is a point which is exceedingly difficult to determine in 
the present instance. 
So far as they go, therefore, my observations speak very 
decidedly against the origin of the chromosomes of this plant from 
the approximated sides of loops, and they agree much more nearly 
with the views of the Bonn and Louvain schools. 
Another interesting feature which is very nicely shown in these 
nuclei is the fate of the chromosomes during the telophase of the 
division. 
It will be recollected that until recently most cytologists 
believed that during the telophase of division the chromosomes 
became joined end to end, and that the filament which was thus 
formed became gradually thinner and longer and coiled in every 
direction through the nuclear-cavity. The coils anastomosed with 
one another so that finally the chromatic contents of the nucleus 
formed a reticulum. 
Gregoire and his pupils have, however, shown that in several 
cases at any rate there is no such end-to-end arrangement of the 
chromosomes during the reconstruction of the daughter-nuclei, but 
that the chromosomes become united by lateral branches which are 
spun out between them, and that at the same time they become 
more and more vacuolated. The resting daughter-nucleus, therefore, 
possesses an alveolar-reticulate structure. The series of changes 
which the chromosomes undergo during the reconstruction of the 
daughter-nuclei in Equisetum are quite like those described by 
Gregoire. At the conclusion of the anaphases the chromosomes 
are seen to be very closely packed together. After the nuclear 
membrane is formed the chromosomes begin to separate from one 
