NOTES. 473 



is again, perhaps, connected in tlie same way with the enperficial 

 form. 



79 (i. 241). The Gustmlation of the varions classes of 

 animals has been far too little studied to enable ns thoroughly 

 to summarize the distribution of the various forms withir the 

 separate classes. Yet it is already evident that primordial egg- 

 cleavage and the formation of the Archigastrula occur in the 

 lowest classes of each tribe. 



80 (i. 243). The Rhythm of egg-cleavage is by no means as 

 regular as might appear from the four first examples in the five 

 tables. There are, on the contrary, many variations, and not 

 infrequently an entirely irregular and very variable sequence of 

 numbers occurs (especially in discoided cleavage). 



81 (i. 246). Definition of the Type. Cf. Gegenbanr, 

 '' Elements of Comparative Anatomy," 1874, p. 59. 



82 (i. 246). Types and Phyla. AccordiDg to the prevailing 

 " Type- theory," the types of the animal kingdom are parallel, 

 and entirely independent ; according to my " GastraBa- theory," 

 on the contrary, they are divergent tribes, connected at the 

 roots ; according to the view of Glaus and other opponents, the 

 latter is no essential distinction. 



83 (i. 248). The one-ceUed condition of Infusoria entirely 

 forbids their morphological comparison with Metazoa. Cf. my 

 article " On the Morphology of Infusoria " (" Jen. Zeitschrift 

 fiir Naturwissenschaft " 1873, vol. vii. p. 516-568). 



84 (i. 257). The axes of the Vertebrate outline. Cf. my 

 " Promorphology " (Stereometry of Organisms). — " Generelle 

 Morphologic," vol. i. pp. 374-574. " Singly double-outlines " 

 (Dipleura), p. 519. "Bilateral-symmetrical" forms in the fourth 

 signification of the word. 



85 (i. 255). The Primitive Vertebrate Type, as it is repre- 

 sented in Figs. 52-56, is a hypothetic diagram, which is principally 

 founded on the outline of the Amphioxus, but^ in which the 

 Comparative Anatomy of Ascidia and Appendicularia on the 

 one side, of Cyclostomi and Selachii on the other, is regarded 

 This diagram is by no means meant to be an " exact figure," but 



