638 WILSON. 



PLATE XXXVIII. 



[From preparations. Figs. 136 to 140 enlarged 225 diameters; the others 270 diameters.] 



Fig. 136. Normal larva at the stage of the first gill-slit, 48 hrs. 



Fig. 137. Half-sized dwarf (probably a Y4 embryo) derived from shaken 

 4-celled stages (48 hrs.). 



Fig 138. Half-sized dwarf (^ embryo) from isolated ^ blastomere. From the 

 same spawning as Fig. 136 (48 hrs.). 



Fig. 139. Fourth-sized dwarf (^ embryo) from a blastomere of the 4-celled 

 stage. From the same spawning as Fig. 137 (48 hrs.). The larva shows several 

 defects. 



Fig. 140. Double monster, from shaken 2-celled stage (48 hrs.). 



Fig. 141. Normal segmented larva (16 hrs.). 



Fig. 142. Half-sized dwarf (^ embryo) from a blastomere of the 2-celled 

 stage. From the same set of eggs as the last (16 hrs.). 



Fig. 143. Fourth-sized dwarf (^ embryo) from a blastomere of the 4-celled 

 stage. The notochord is shown, but the somites could not be distinguished. 



Fig. 144. Double monster, from the same set as Fig. 142. The anterior 

 extremities free. 



