NOTES. 489 



The palin genetic germination of Selacliii has been mucli altered 

 by kenogenetic adaptations. 



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

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

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

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

 important distinction of homology (morphological resemblance) 

 and Analogy (physiological resemblance), see Gegenbanr, as 

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



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

 Groove in Tiinicates, and its Presence in the Amphioxns and 

 Cyclostomi." — " Jenaische Zeitschrift fiir Naturwissenschaft," 

 1873, Tol. viii. p. 327. 



190 (ii. 358). The Nerve-mnscular 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" 

 ("Entwickelungsgeschiohte 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 

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

 operation between Comparative Anatomy and Ontogeny. Cf. 

 Geo-enbaur on Comparative Anatomy (" Grundriss der verglei- 

 chenden Anatomie "). 



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

 functions of reprodiiction and of heredity, connected with re- 

 production, are referable to gi'owth, so the former as well as the 



