They alternate, but do not merge into one another to produce intermediate forms.

Indeed, we see intermediate forms and species corresponding to intermediate conditions.

At any rate, the absence of intermediate forms is no argument in favour of it.

Here various intermediate forms may be the most abundant.

These intermediate forms are, at present, the store on which the artist has to draw.

At another place, speaking of intermediate forms he says:-

For our genealogical purposes the most interesting are the intermediate forms between the Selachii and the Dipneusts.

Their origin is not clear, as the intermediate forms between them and the amphibia are not found.

There are lordships and principalities which are bought and sold, and some other intermediate forms of government.

Speaking elsewhere of intermediate forms, he remarks:-

R. hallense and R. hirsutiforme are intermediate forms of a natural cross between R. hirsutum and R. ferrugincum.

Some intermediate forms still record to us the long struggle during which the schism was not yet complete.

The disappearance of intermediate forms naturally leads up to the subject of extinction, with which the next extract begins.

There are no intermediate forms.

Just as we come to know them better, intermediate forms flow in, and doubts as to specific limits augment.

In other words, no intermediate forms which bridge over these gaps or intervals are, at present, to be met with.