1. Internally viviparous Sanguinea } producing a perfect 2. Externally viviparous Sanguinea } animal. 3. Oviparous Sanguinea--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_ in the Oxford series. [6] On Aristotle's forerunners, see R. Burckhardt, "Das koische Tiersystem, eine Vorstufe des zoologischen Systematik des Aristoteles." _Verh. Naturf. Ges. Basel_, xx., 1904. [7] T.E. Lones, _Aristotle's Researches in Natural Science_, pp. 82-3, London, 1912. [8] _De Partibus Animalium_, i., 4, 644^a trans. W. Ogle, Oxford, 1911. CHAPTER II