„ „ Zur Entwickelung von Bythinia tentaculata: Mitth. Zool. Stat. Neap, x. (1892), pp. 376–406. =H. Fol=, Sur le développement des Ptéropodes: Arch. Zool. exp. gén. iv. (1875), pp. 1–214. „ Etudes sur le développement des Mollusques. Hétéropodes: ibid v. (1876), pp. 105–158. „ Etudes sur le développement des Gastéropodes pulmonés: ibid. viii. (1880), pp. 103–232. =H. Grenacher=, Zur Entwickelungsgeschichte der Cephalopoden: Zeit. wiss. Zool. xxiv. (1874), pp. 419–498. =B. Hatschek=, Ueber Entwickelungsgeschichte von Teredo: Arb. Zool. Inst. Univ. Wien, iii. (1881), pp. 1–44. =R. Horst=, On the development of the European oyster: Quart. Journ. Micr. Sc. xxii. (1882), pp. 339–346. =E. Korschelt= and =K. Heider=, Lehrbuch der vergleichenden Entwickelungsgeschichte der wirbellosen Thiere, Heft iii. (1893), pp. 909–1177 (the work is in process of translation into English). =A. Kowalewsky=, Embryogénie du Chiton polii avec quelques remarques sur le développement des autres Chitons: Ann. Mus. Hist. Nat. Mars. Zool. i. (1883), v. =E. Ray Lankester=, Contributions to the developmental history of the Mollusca: Phil. Trans. Roy. Soc. vol. 165 (1875), pp. 1–31. „ „ Observations on the development of the pond-snail (Lymnaeus stagnalis), and on the early stages of other Mollusca: Quart. Journ. Micr. Sc. xiv. (1874), pp. 365–391. „ „ Observations on the development of the Cephalopoda: ibid. xv. (1875), pp. 37–47. =W. Patten=, The embryology of Patella: Arb. Zool. Inst. Univ. Wien, vi. (1886), pp. 149–174. =M. Salensky=, Études sur le développement du Vermet: Arch. Biol. vi. (1885), pp. 655–759. =L. Vialleton=, Recherches sur les premières phases du développement de la Seiche (Sepia officinalis): Ann. Sc. Nat. Zool. (7) vi. (1888), pp. 165–280. =S. Watase=, Observations on the development of Cephalopods: Stud. Biol. Lab. Johns Hopk. Univ. iv. (1888), pp. 163–183. „ „ Studies on Cephalopods: Journ. Morph. iv. (1891), pp. 247–294. =E. Ziegler=, Die Entwickelung von Cyclas cornea Lam.: Zeit. wiss. Zool. xli. (1885), pp. 525–569. CHAPTER VI RESPIRATION AND CIRCULATION--THE MANTLE The principle of respiration is the same in the Mollusca as in all other animals. The blood is purified by being brought, in successive instalments, into contact with pure air or pure water, the effect of which is to expel the carbonic acid produced by animal combustion, and to take up fresh supplies of oxygen. Whether the medium in which a mollusc lives be water or air, the effect of the respiratory action is practically the same.