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Figs. 200-215.— Development of lamprey, Petromyzon planeri. Figs. 200-204, 208-212 
_ & 18, others x ut 30. 200, 201. First cleavage, beginning and concluded. 202. Third 
oe: 203. Fourth cleavage, in section, showing Man nage of segmentation cavity. 204, 
2 ly and late blastulz, in section, 206, 207. Early and late gastrule, in section. 208, 
_ 210, 212. Early embryos showing growth of head end. 209, 211. Sagittal sections of early 
@ wot fab, rentiation of organs. 213, 214. Transverse sections of early embryos. 
«25. on of newly hatched larva, Ammocetes. (Figs. 211, 215, after GOETTE, others 
after V. KUPFFER.) 
BP. Biastopore. C. Coelenteron. CH. Notochord. DZ. Dorsal lip of blastopore. EC. 
NV. Entoderm. ZF. Epiphysis. G. Gut. #. Heart. 4. Central nervous 
MES. Mesoblast. N. Nasal pit. MC. Neurenteric region. S. Mouth pit, stomo- 
SC. Segmentation cavity. 7. Thyroid gland. Y. Yolk and yolk cells. 
189 
>» 
