Pl. F. 
HUBRECHT. 
33 
35 36 
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34 
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37 38 
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Fig. 33, 34 and 35. Sections of quite early stages of the hedgehog’s 
blastocyst. Zr trophoblast, ex entoderm, ¢c ectoderm yet firmly united with the 
trophoblast. — Fig. 36. A somewhat later stage in which considerable lacunae 
have originated in the proliferating trophoblast into which maternal blood 
penetrates. — Fig. 37. Section through a yet later stage in which the lacunae 
haye developed all round the blastocyst and in which the amnion cavity (a) 
has arisen as a split between trophoblast and embryonic ectoderm (cc). — Fig. 38. 
Yet later stage of the hedgehog’s blastocyst in which the development of the 
embryo is further advanced and the amnion-wall completed and externally 
clothed by mesoblast. 2 umbilical vesicle, co coelom. 
