me or collateral
lines. The fact that two organisms belong to the same line of descent is
recognized from the ontogeny of the higher including the ontogeny of the
lower.

Since only a proportionately small number of known forms can appear as
types of the supposed stages of evolution, only a few phylogenetic
lines, and these only in a general way, may be established, on account
of the great incompleteness of the present plant world. Such a line
proceeds from the green filamentous algae through the liverworts to the
vascular plants. Among the phanerogams, apparently so numerously
represented, only phylogenetic series of individual organs can be
ascertained, but no phylogenetic series of families. A phylogenetic
system of phanerogams is not to be hazarded in the roughest outline.
Even the relative rank of the two chief divisions of the angiosperms,
the monocotyledons and dicotyledons, is a matter of question, as also
which family in each of these divisions is to be considered the most
perfect.

APPENDIX.

TRANSLATORS' NOTES.

_The Mechanico-physiological Theory of Evolution_,
(_Mechanisch-Physiologische Theorie der Abstammungslehre_),
by Carl von Naegeli, was published in Munich and Leipsic in 1884 in a
large octavo volume of 822 pages, including two large appendices. The
_Abstammungslehre_ proper, including the summary, occupies 552 pages,
and constitutes, in its way, one of the most important contributions to
theoretical biology. It is difficult to understand how a work of so much
consequence should have received such comparatively small notice in this
country, especially as Naegeli's theories seemed calculated by nature to
appeal much more strongly to American students than do, for instance,
those of Weismann, who has been studied ten times as much as Naegeli.
This is doubtless due, in part, to the fact that we have had no English
translation of Naegeli's work, a circumstance much to be regretted.

The foregoing translation of the summary from _Abstammungslehre_
goes but a small way toward making Naegeli's theories accessible to
English-reading students, but it will, at least, be better than nothing.
The work covers a great range of subjects, all, however, having a
certain relationship to each other. In the main part of the book the
discussion is presented in the following order: (1) Idioplasm as bearer
of the inheritable determinants; (2) Spontaneous generation; (3) Causes
of variation; (4) Determinants