NOTES. 489 



The palin genetic germination of Selachii has been much altered 

 by kenogenetic adaptations. 



188 (ii. 323). On the Homology of Scales and Teeth, cf. 

 Gegenbaur, " Comparative Anatomy " (" Grnndriss der vergl. 

 Anatomie," 1874, pp. 426, 582) ; also Oscar Hertwig, " Jenaische 

 Zeitschrift fur Naturwissenschaft," 1874, vol. viii. On the 

 important distinction of homology (morphological resemblance) 

 and Analogy (physiological resemblance), see Gegenbaur, as 

 above, p. 63; also my " Generelle Morphologie," vol. i. p. 313. 



189 (ii. 337). Wilhelm Miiller, "On the Hypobranchial 

 Groove in Tunicates, and its Presence in the Amphioxus and 

 Cyclostomi." — "Jenaische Zeitschrift fur Naturwissenschaft," 

 1873, vol. viii. p. 327. 



190 (ii. 358). The Nerve- muscular Cells of the Hydra throw 

 the earliest light on the simultaneous, phylogenetic differentiation 

 of nerve and muscle tissue. Cf. "Klemenberg, Hydra." Leipzig, 

 1872. 



191 (ii. 383). The germ-history of the human heart accurately 

 reproduces in all essential points its tribal history. This palin- 

 genetic reproduction is, however, much contracted in particular 

 points and vitiated by kenogenetic modifications of the original 

 course of evolution, displacements partly in time, partly in place, 

 which are the result of embryonic adaptations. 



192 (ii. 383). On the Special Germ-history of the Human 

 vascular system, cf. Kolliker, "History of the Evolution of Man" 

 ("Entwickelungsgeschichte des Menschen." 2nd edition, 1876) ; 

 also Rathke's excellent work on Ontogeny. 



193 (ii. 387). The Homologies of the Primitive Organs, as 

 they are here provisionally described in accordance with the 

 Gastrasa- theory (note 24), can only be established by further co- 

 operation between Comparative Anatomy and Ontogeny. Cf. 

 Gegenbaur on Comparative Anatomy (" Grundriss der verglei- 

 chenden Anatomie "). 



194 (ii. 390). The Mechanism of Reproduction. As the 

 functions of reproduction and of heredity, connected with re- 

 production, are referable to growth, so the former as well as tho 



