500 
L. DOXCASTER AND J. GRAY. 
div’ision all the chromosomes have usually regained their 
normal behaviour. When widely different numbers are counted 
at the two poles of one spindle in the later segmentation 
divisions (cf. fig. 27 a, h), it is possible that some chromo- 
somes are still behaving abnormally, but another possible 
explanation is that owing to the irregularity of the equatorial 
plate the two halves of the chromosomes are still seen in one 
daughter-plate. 
Comparing these conclusions with what has been described 
in the cross acutus ? x esculentusJ'jit is seen that in 
the latter cross a similar tendency is more strongly shown; 
some chromosones swell up entirely to vesicles which are left 
out of the spindle, and others produce smaller vesicles, and 
in some cases probably fail to divide. 'I’he vesicles which 
are left near the equator of the spindle are eliminated. 
In the second division there is already evidence that the 
chromosomes are beginning to recover, and the results 
obtained from the cross acutus ? x miliaris S suggest 
that in the later segmentation divisions their behaviour 
would again be normal. Owing, however, partly to the 
elimination of some entire chromosomes in the first division, 
and to the failure of others to divide, the chromosome 
number of the acutus ? x esculentusc? hybrid would 
be reduced from 38 to somewhere between 31 and 37, the 
number varying in different embiyos, and probably some- 
times in different cells of the same embryo. 
The preceding account deals with the hybrid eggs obtained 
in 1911. In that year, owing to an oversight, no eggs of 
suitable age were obtained fi'om the crosses esculentus ? 
X miliaris J' > fmd of miliaris ? x esculentus and 
acutus cJ . These hybrids were obtained in 1912, but, as 
Shearer, De Morgan and Fuchs have recorded,^ the plutei 
obtained from them differ considerably from those reared in 
1911, and the miliaris eggs especially appear in this year to 
develop much less satisfactorily than in 1911. It cannot, 
‘ ‘Xature,' June 27th, 1912. 
