NOTES. 469 



mentella, or cleavage-cells, which constitute the Morula at the 

 close of palingenetic egg-cleavage, generally appear entirely 

 similar, with morphological difference in size, form, or con- 

 stitution. This does not, however, hinder the fact that these 

 cells have separated, even during cleavage, into animal and 

 vegetable cells, have differentiated physiologically, as is indicated 

 in Figs. 2 and 3, Plate II., as probable. 



61 (i. 189). The Bladder-germ of Archiblastic Animals 

 (blastula, or blastosphcera*), which is now commonly known as 

 the germ-vesicle, or, more accurately, as the " germ-membrane 

 vesicle," must not be confused with the essentially different 

 " germ- vesicle " of amphiblastic mammals, which is better called 

 the "intestinal-germ vesicle" (gastrocystis'). The gastrocystis 

 and the blastula are still often united under the name of " germ- 

 vesicle, or vesicula blastodermica." Cf. vol. i. p. 290. 



62 (i. 192). The Definition of the Gastrnla was first 

 established by me in 1872, in my "Monograph of Chalk-sponges " 

 (vol. i. pp. 333, 345, 466). There I already gave due weight to 

 the " extremely great significance of the gastrula in reference 

 to the general Phylogeny of the animal kingdom" (p. 333). 

 " The fact that these larval forms re-occur in the most different 

 animals, cannot, I think, be sufficiently estimated, and bears 

 plain witness to the former common descent of all from the 

 G-astrsea " (p. 345). 



63 (i. 194). The Uniaxial Outline of the Gastrula is, on 

 account of the two different poles of the axis, more accurately 

 described as a diplopolic uniaxial form (a sternometric outline : 

 conoid-form, or cone). Cf. my " Promorphology " (" Generelle 

 Morphologic," vol. i. p. 426). 



64 (i. 194). Primitive Intestine and Primitive Mouth. My 

 distinction of the primitive intestine and primitive mouth 

 (protogaster and proiostoma) from the later, permanent intestine 

 and mouth (metagaster and metastoma) has been variously 

 attacked ; it is, however, as much justified as the distinction of 

 the primitive kidney from the permanent kidney, of the primitive 

 vertebrae from the permanent vertebrae. The primitive intestine 



