[33] The recent researches of Pringsheim have raised a host of questions as to the exact share taken by chlorophyll in the chemical operations which are effected by the green parts of plants. It may be that the chlorophyll is only a constant concomitant of the actual deoxidising apparatus. [34] “Researches in the Life-history of a Cercomonad: a Lesson in Biogenesis;” and “Further Researches in the Life-history of the Monads.”—“Monthly Microscopical Journal,” 1873. [35] Excellently described by Stein, almost all of whose statements I have verified. [36] “Histoire des Sciences Naturelles,” i. p. 152. [37] The text I have followed is that given by Aubert and Wimmer, “Aristoteles Thierkunde; kritisch berichtigter Text mit deutschen Uebersetzung;” but I have tried here and there to bring the English version rather closer to the original than the German translation, excellent as it is, seems to me to be. [38] In modern works on Veterinary Anatomy the lungs are sometimes described as two lobes of a single organ. [39] “Histoire des Sciences Naturelles.”—t. i. p. 130. [40] “Aristotle, a Chapter from the History of Science.” [41] I quote, here and always, Cousin’s edition of the works of Descartes, as most convenient for reference. It is entitled “Œuvres complètes de Descartes,” publiées par Victor Cousin. 1824. [42] “Les Passions de l’Âme,” Article xxxiii. [43] “Recherches physiologiques sur la Vie et la Mort.” Par Xav. Bichat. Art. Sixième. [44] Locke (_Human Understanding_, Book II., chap. viii. 37) uses Descartes’ illustration for the same purpose, and warns us that “most of the ideas of sensation are no more the likeness of something existing without us than the names that stand for them are the likeness of our ideas, which yet, upon hearing, they are apt to excite in us,” a declaration which paved the way for Berkeley. [45] “Passions de l’Âme,” Art. xxxvi. [46] “Quamcumque Bruti actionem, velut automati mechanici motum artificialem, in eo consistere quod se primò sensibile aliquod spiritus animales afficiens, eosque introrsum convertens, _sensionem_ excitat, à qua mox iidem spiritus, velut undulatione reflexâ denuo retrorsum commoti atque pro concinno ipsius fabricæ organorum, et partium ordine, in certos nervos musculosque determinati, respectivos _membrorum motus_ perficiunt.”—WILLIS: “De Animâ Brutorum,” p. 5, ed. 1763. [47] “Les Passions de l’Âme,” xlii. [48] Haller, “Primæ Lineæ,” ed. iii. “Sensus Interni,” dlviii. [49] “Réponse de M. Descartes à M. Morus.” 1649. “Œuvres,” tome x. p. 204. “Mais le plus grand de tous les préjugés que nous ayons retenus de notre enfance, est celui de croire que les bêtes pensent,” etc.