The Embryology of Patella. 
25 
Plate II. 
Fig. 19. Embryo in tbe blastosphere stage, seen as a semi-transparent object. 
(10 hours.) 
Fig. 20. Embryo at the end of the blastosphere stage, showing four large 
endoderm cells en 1 . en 1 . en 3 . en''. and the laterally placed cells en. m. which give 
rise to the primitive mesoderm cells. (12 hours.) 
Fig. 21. Embryo of 14 hours ; it has just escaped from the chorion. 
Fig. 22. Section of an embryo of 14 hours, showing first cross division of 
the endoderm cells en'. en". 
Fig. 23. Dorso-ventral section tbrough the blastopore of an embryo of 
14 hours, showing the primitive mesoderm cell before it has separated itself from 
the cell en. m. on the edge of the blastopore. 
Fig. 24. Dorso-ventral section through an embryo of 15 hours, showing the 
primitive mesoderm cell p. m. just after its division from the parent cell en. m. 
Fig. 25. Longitudinal section through an embryo of 18 hours. 
Fig. 26. Embryo of 20 honrs, seen as an opaque object. 
Fig. 27. Median dorso-ventral section of an embryo of 24 hours. The blasto¬ 
pore has become slightly eccentric. 
Fig. 28. Posterior end of an embryo of 14 hours, showing four endoderm 
cells in the blastopore. 
Fig. 29. Posterior end of an embryo of 26 hours with ventrally placed 
blastopore. 
Fig. 30. Posterior end of an embryo of 28 hours with still more ventrally 
placed blastopore. 
Fig. 31. Embryo of 30 hours seen as an opaque object. 
Fig. 32. Dorso-ventral section through an embryo of 28 hours with ventrally 
placed blastopore. 
Plate III. 
Fig. 34. Embryo of 34 hours seen from the ventral surface showing the 
blastopore at the apex of the Y-shaped furrow. 
Fig. 35. Embryo about 2 hours older showing the very small blastopore 
in the semicircular area on the ventral surface of the embryo. 
Fig. 36. Embryo of 34 hours seen from dorsal surface, showing the primitive 
mesoblast cells and the pecnliar conformation of the posterior row of velar cells. 
Fig. 37. Embryo of 40 hours seen from the ventral surface, showing a 
stage in the transformation of theV-shaped furrow into the opening of the Oeso¬ 
phagus. The primitive mesoblast cells have given rise to two new mesoderm cells. 
Fig. 38. Shows the transformation of the anterior end of the V-shaped 
furrow into the mouth opening. 
Fig. 39. Embryo of 40 hours seen from the dorsal surface. 
Fig. 40- Section through the blastopore of an embryo of 30 hours. a, cell 
probably arising from a second division of the parent cells of the primitive 
mesoblast. 
Fig. 41. Section through the blastopore of an embryo of 40 hours, showing 
the blastopore shortly before it closes. 
Fig. 42- Embryo of 44 hours seen from the ventral side ; the ventral furrow 
v. f. still marks the place where the V-shaped depression formerly existed. 
Fig. 43. Basal end of an embryo of 25 hours. 
Fig. 44. Cross section through the sliell gland of an embryo of 45 hours. 
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