Origin of Species Variorum

→ having 1859 1860 1861 1866 1869

including of course the reproductive systems, having 1872

→ rarely diminishes. 1859 1860 1861

does not diminish, but is apt to increase; this increase being perhaps intelligible, as before explained, on the principles of inheritance and from too close interbreeding. 1866

does not diminish; it is even apt to increase, this being generally the result, as before explained, of too close interbreeding. 1869 1872

↑ 1 blocks not present in 1859 1860 1861; present in 1866 1869 1872

The above view of the sterility of hybrids being caused by two different constitutions being confounded into one has lately been strongly maintained by Max Wichura; but it must be owned that the sterility but it must be owned that the sterility (as will be immediately explained) which affects the offspring of dimorphic and trimorphic plants, when individuals belonging to the same form are united, makes this view rather doubtful. which affects the offspring of dimorphic and trimorphic plants, but it must be owned that the sterility (as will be immediately explained) which affects the offspring of dimorphic and trimorphic plants, when individuals belonging to the same form are united, makes this view rather doubtful. the same but it must be owned that the sterility (as will be immediately explained) which affects the offspring of dimorphic and trimorphic plants, when individuals belonging to the same form are united, makes this view rather doubtful. makes this view rather doubtful.

→ vague hypotheses, 1859 1860 1861

this or any other view, 1866

the above or any other view, 1869 1872

→ having 1859 1860 1861 1872

or constitution having 1866 1869

are produced by the unnatural crossing of two species, the reproductive system, independently of the general state of health, is affected

~~by sterility~~

by sterility

in a very similar manner. In the one case, the conditions of life have been disturbed, though often in so slight a degree as to be inappreciable by us; in the other case, or that of hybrids, the external conditions have remained the same, but the organisation has been disturbed by two

distinct

different

structures and

constitutions,

constitutions

→having been blended into one. For it is scarcely possible that two organisations should be compounded into one, without some disturbance occurring in the development, or periodical action, or mutual

relations

relation

of the different parts and organs one to

another

another,

or to the conditions of life. When hybrids are able to breed inter

se,

se ,

they transmit to their offspring from generation to generation the same

com- pounded

compounded

organisation, and hence we need not be surprised that their sterility, though in some degree

vari- able,

variable,

→rarely diminishes. ↑

must

must,

also

~~however,~~

however,

owned

confessed

that we cannot understand,

excepting

~~except~~

except

on →vague hypotheses, several facts with respect to the sterility of hybrids; for instance, the unequal fertility of hybrids produced from reciprocal crosses; or the increased sterility in those hybrids which occasionally and exceptionally resemble closely either pure parent. Nor do I pretend that the foregoing remarks go to the root of the

matter;

matter:

no explanation is offered why an organism, when placed under unnatural conditions, is rendered sterile. All that I have attempted to

show

show,

is,

that in two cases, in some respects allied, sterility is the common

result, —

result,—in

result,—

the one case from the conditions of life having been disturbed, in the other case from the organisation →having been disturbed by two organisations

being

having been

compounded into one.