142 
'riios. II. Montgomerj% jr. 
some could be rccogiiized in every mitosis ; but we may reply that an equa- 
tional division of certain univalent cliromosomes is thorouglily demon- 
strated in tbe case of certain diplosomes (idiochroniosomes) of Hemiptera, 
and that it is not necessary to recognize every one of the chromosomes, 
for if the observer can recognize any one of themwith certainty, and deter- 
niine its continnity from generation to generation, by the argument of 
analogy the others inay be concluded to behave in the same way: the 
crncial cases are not those, such as Salamandra, where peculiarities of the 
several chromosomes cannot be distingiiished, but those numerous other 
cases, particularly in insects, where constant size and form differences of 
the chromosomes can be positively recognized. It is not stränge that the 
objectors to the theory of chromosomal continnity have each of them 
failed to make first hand studies of particularly decisive cases in insect 
spermatogenesis. 
Or the chromosomal number may be one less than the normal which 
has sometimes been explained by incomplete Segmentation of the spirem 
thread. Della Valle objects to this the conclusion of Gregoire, that 
there is no continuous spii’em thread; we may answer that this is the case 
only after the conjugation of the chromosomes, while oögonia and sperma- 
togonia seem to possess continuous spirem threads. Again a number less 
than the normal has been explained by the disappearance of a particular 
niember. Della Valle States this argument would be a tautology, if 
one could recognize all the chromosomes; butwe may reply that itis not 
necessary to recognize all of them, it is sufficient to positively ascertain 
the disappearance of a particular recognizable one. Or chromosomal 
number less than the normal has been explained on the ground of chro- 
mosome complexes. Della Valle objects that this begs the whole que- 
stion; but he seems to have wholly misunderstood the rather numerous 
cases of chromosonie complexes, for in these cases we find dose juxtappo- 
sitions of clmomosomes but no fusion of their substance, the single com- 
ponents of each such complex may always be distingiiished. 
All through Ins argument Della Valle, like the other opponents to 
the theory of the individuality of the chromosomes, exhibits a pronounced 
scepticism towards the cases of the modified chromosomes, allosomes, 
which furnish one of the strengest arguments to the theory. They are 
sufficiently answered wlien we recall that not one of these critics has per- 
sonally exaniined a case of a cell containing allosomes. Della Valle 
practically disregards these modified chromosomes. 
His objection that the chromosomes cannot be persisting individuals 
because they are Chemical botlies nndergoing metabolism, would be 
