CIIROI\IOSOMES, HEREDITY AND SEX. 
495 
in both the reciprocal crosses, this result would be expected 
if the Hippoiioe characters were dominant.^ 
Indications of the same sort, but somewhat less direct, 
have been given by Herbst (25). He has found in occasional 
hybrids between S phmrechi nus $ and S tron gylocen- 
trotus (^ , individuals with purely Spliyerechiuus skeleton 
on one side, and intermediate skeleton on the other. On the 
side with Spheerec h i n us skeleton the nuclei have half the 
volume of those on the other side, indicating* that they 
contain fewer chromosomes, and he supposes that the sper- 
matozoon has conjugated with one of the nuclei of the first 
two blastomeres, so that half the larva has purely maternal, 
the other half hybrid nuclei. 
Evidence of this kind, while not proving that the chromo- 
somes are directly concerned in the transmission of inherited 
characters, makes such a hypothesis very plausible.^ Much 
unnecessary confusion, however, has arisen, from stating the 
hypothesis in the form — the chromosomes are probably the 
bearers of inherited characters. Evidence has been adduced 
that the cytoplasm plays some part in determining these 
characters, and it has therefore been maintained that the 
statement is disproved. No one, however, would suppose that 
the chromosomes could act alone ; they must act in and by 
their relation with the cytoplasm, and if the cytoplasm is 
that of a different species, the total effect must necessarily be 
different. A simple chemical analogy will make this clear. 
The substance represented CH.^H is a hydrocarbon ; exchange 
' The writer and J. Gray (‘ Quart. Jonrii. Micr. Sci.,’58, 1913, p. 483) 
found elimination of one or two chromosomes in the cross Echinus 
miliaris $ X E. acutns , but none in the converse cross. In the 
case of the cross E. acutns $ x E.escnlentns (j', in which some 
chromosomes are lost by becoming vesicular and failing to divide, there 
is evidence that the vesicular chromosomes are maternal (J. Gray, 
‘ Quart. Journ. Micr. Sci.,’ 58, 1913, p. 447). In these cases it was not 
found possible to correlate the chromosome behaviour with the inherited 
characters of the plutei. 
’ The evidence adduced by Goldschmidt (‘ Arch. Zellforsch.,’ ix, 1912, 
p. 331) has not been mentioned, since its correctness has been disputed 
(O. Renner, ‘ Berichte d. deutsch. Botan. Gesellsch.,’ xxxi, 1913, p. 334). 
