uinea--producing a perfect egg.
4. Animals producing an imperfect egg (one which
increases in size after being laid).
5. Insects, producing a scolex (or grub).

In Aristotle's view the gradation of organic forms is the consequence,
not the cause, of the gradation observable in their activities. Plants
have no work to do beside nutrition, growth, and reproduction; they
possess only the nutritive soul. Animals possess in addition sensation
and the sensitive or perceptive soul--"their manner of life differs in
their having pleasure in sexual intercourse, in their mode of
parturition and rearing their young" (_Hist. Anim._, viii., trans.
Cresswell, p. 195). Man alone has the rational soul in addition to the
two lower kinds.

As it is put in the _De Partibus_ (ii., 10, 656^a, trans. Ogle),
"Plants, again, inasmuch as they are without locomotion, present no
great variety in their heterogeneous parts. For, where the functions
are but few, few also are the organs required to effect them....
Animals, however, that not only live but feel, present a greater
multiformity of parts, and this diversity is greater in some animals
than in others, being most varied in those to whose share has fallen
not mere life but life of high degree. Now such an animal is man."

With the great exception of Aristotle, the philosophers of Greece and
Rome made little contribution to morphological theory. Passing mention
may be made of the Atomists--Leucippus, Democritus, and their great
disciple Lucretius, who in his magnificent poem "De Natura Rerum" gave
impassioned expression to the materialistic conception of the
universe. But the full effect of materialism upon morphology does not
become apparent till the rise of physiology in the 17th and 18th
centuries, and reaches its culmination in the 19th century. The
evolutionary ideas of Lucretius exercised no immediate influence upon
the development of morphology.

[1] E. Zeller, _Greek Philosophy_, Eng. trans., i., 522
f.n., London 1881. Other particulars as to Alcmaeon in
T. Gomperz, _Greek Thinkers_, Eng. trans., i., London,
1901.

[2] Zeller, _loc. cit._, i., p. 297.

[3] Gomperz, _loc. cit._, i., p. 244.

[4] R. Burckhardt, _Biologie u. Humanismus_, p. 85,
Jena, 1907.

[5] See the interesting account of Aristotle's
biological work in Prof. D'Arcy W. Thompson's Herbert
Spencer lecture (1913) and his translation of the
_Historia Animalium