io6 



CLEAVAGE AND DIFFERENTIATION 



•Fig. 49 

 Mosaic development of Ctenophores. A, i6-cell stage divided into two equal 

 lateral halves. B, Partial larvae developed from these halves; each has four 

 costae. c, cilia; e, endoderm;/, fold in egg-case showing line of division of the 

 halves ; /?, egg-case ; tn, stomach ; ;/, nerve centre ; ot, otolith ; p, pigment ; r, costae. 

 (After Fischel, from Schleip, Determination der Primitivetitzvicklung, 1929, fig. 18, 

 P- 5I-) 



