49G 
L, DONCASTER AND J. GRAY. 
result that the chromosomes are more crowded ; this relative 
narrowness may be due partly to the absence of divided poles, 
which in the esc ulentus hybrids cause considerable widening 
of the whole figure, but this cannot completely account for 
the difference, for in the exceptional cases of divided poles in 
the miliar is cross, the spindles are still very narrow. The 
general appearance of the spindles and asters is mncb more 
like that of pure mi liar is than of acutus, suggesting that 
the centrosome introduced by the mi 1 iaris spermatozoon can 
cause mitotic figures of the miliaris type to develop in 
acutus eg’gs. Our observations on the hybrid eggs have been 
made almost entirely on two lots, which gave in seme respects 
dissimilar results. One lot consists of stages from the 
beginning of the first to the beginning of the second segmen- 
tation division, all the stages of the first division being well 
represented. The second lot contains much more advanced 
eggs, up to the 16-cell stage at least, but also includes 
early stages from prophases of the first segmentation division 
onwards. In a preliminary examination of the first lot we 
failed to find any trace of elimination or of vesicle formation; 
both equatorial plates and anaphases were somewhat irregular, 
but the conspicuous vesicles found in the acutus $ x 
esculentus cross appeared quite absent. In the second 
lot, however, vesicles were not rarely found in the earlier 
divisions, and when present were of the same kind and as 
conspicuous as in the cross with esculentus cJ . A re- 
examination of the second lot showed that vesicles were 
sometimes pi-esent, but were in most cases very small, and 
attached to chromosomes as in prophases of the acutus ? x 
esculentus cross (fig. 22). Further, in metaphase and 
early anaphase it is sometimes, though not by an\- means always, 
possible to see that a few (one to three) chromosomes are 
swollen, irregular in shape, and without any trace of a 
division at a time when the halves of the remainder are 
beginningto separate. In later anaphases the majority of the 
chromosomes are rod-shaped, long and narrow, but sometimes 
a few are much larger and more ovoid in shape. In anaphases 
occasionally a minute vesicle may be seen left on the spindle. 
