492 
L. DONCASTER AND J. GRAY. 
spermatozoon, but an examination of a series shows that every 
stage occurs between normal spindles, through those with 
poles just divided to examples with four, or sometimes three 
quite distinct spheres to which the fibres converged A further 
difference is that in no case have we found a noticeably 
abnormal number of chromosomes ; sometimes they appear 
to be considerably below the normal number, due doubtless 
to “ clumping,” but never conspicuously above the number 
expected. In one batch of eggs of pure esculent us, on the 
other hand, true tripolar and quadripolar spindles are of very 
frequent occurrence, in fact hardly any of the eggs are 
dividing normally ; but in this case the chromosome number is 
constantly about either one and a half times or twice the 
normal (38). For example, in this batch of pure esculentus 
four counts of chromosomes on abnormal spindles (late pro- 
phase) gave respectively 52, 70, 71 and about 65 chromo- 
somes (the numbei’S are only approximate) ; numbers of this 
kind have never occui’red in the acutus $ x esculentus 
^ hybrids. We can only conclude, thei'efore, that in eggs 
of this cross there is a tendency for the centrospheres to 
divide prematurely, but the daughter-spheres rarely separate 
so widely as to cause an abnormal cell division. A moderate 
division of the spheres has been seen in some anaphase 
figures of pure acutus and of the converse cross esculentus 
$ X acutus (J, but in these eggs it is never so extensive as 
in the cross acutus ? x esculentus (J. 
In the prophase of the second segmentation mitosis the 
chromosomes appear within the nucleus as elongated, more or 
less bent rods, like those of the same stage in the first 
division, but the smaller size of the nuclei and frequent 
interlacing of the chromosomes make trustworthy counting very 
difficult. AAithin the nucleus sometimes a varying number of 
faintly stained, round bodies may be seen, which we at first 
took for vesicles which had been included in the nucleus in 
the first telophase, but the inconstancy of their occurrence 
’ Boveri has figured similar divided poles in Echinus micro- 
tuberculatus (‘ Zellenstudien,’ iv, Taf. v, fig. 59). 
