280 GENERAL EMBRYOLOGY 



parts or of blastomeres is not followed by any structural defect. 

 For example, the blastomeres of many Coelenterates (Haeckel, 

 Zoja, Maas, Wilson) may be separated when in the two-, four-, 

 eight-, or even, in some cases, in the sixteen-cell stage, and 

 from such isolated blastomeres typically formed embryos and 

 even free-swimming Iarva3 develop, normal in every respect 

 save that of size, being respectively approximately one-half, one 



FIG. 131. Normal development of one of the blastomeres of the two-cell 

 stage of the Hydroid, Clytia flavidula. After Zoja. A. Two-cells. B. Four- 

 cells. C. Eight-cells. D. Blastula. E. Young polype. 



fourth, one-eighth, or one-sixteenth the normal size (Fig. 131). 

 This is true to a certain extent also of some of the Teleosts and 

 of Amphibians, the Nemerteans, and Echinoderms (Figs. 132, 

 133); in the last named forms even portions of the blastula or 

 gastrula (Driesch) may give rise to normal but diminutive 

 Iarva3 (Fig. 134). It seems very apparent that if cytoplasmic 

 localization occurs at all in such cases, it must be of a very 

 different kind from that described above. 



This is an appropriate place to mention certain experiments 

 of a different kind bearing upon this same problem. Eggs 



