174: DGVclo]-)incnt of '^^Phoi-acio Ycrtebrns in ]\ran 



PLATE V. 



Figs. 17-24. Sagittal sections in the mid-line through the 6th, 7th and 8th 

 thoracic segments of a series of embryos from 12 to 50 mm. long. (17) Em- 

 bryo CCXXI, length 12 mm. This section includes several segments anterior 

 and posterior to the three above mentioned, 6th, 7th and 8th. (18) Embryo 

 CXLIV, length 14 mm. (19) Embryo CVIII, length 22 mm. (20) Embryo 

 LXXXVI, length 30 mm. (21) Embryo CXLV, length 33 mm. (22) Embryo 

 LXXIX, length 33 mm. (23) Embryo XCVI, length 44 mm. (24) Embryo 

 CLXXXIV, length 50 mm. 



PLATE VI. 



Figs. 25-35. Dorsal, lateral and ventral view^s of models made by the Born 

 method to illustrate vertebral form-differentiation in the 6th, 7th and 8th thor- 

 acic vertebrae during the chondrogenous period. On the left side the carti- 

 lagenous, on the right the enveloping fibrous tissue is shown. The latter is 

 also shown on the eighth vertebra in Figures 29 and 35. (25-27) Embryo 

 CXLIV, length 14 mm., 20 diam. (28-30) Embryo XXII, length 20 mm., 

 13 diam. (31-33) Embryo CXLV, length 33 mm., 10 diam. (34, 35) Embryo 

 LXXXIV, length 50 mm., 10 diam. (34) Dorsal view, left half; (35) median 

 view. 



PLATE VII. 



Figs. 36-42. Transverse sections through mid-thoracic vertebrae of a series 

 of embryos. 5 diam. (36) Embryo CVI, length 17 mm. (37) Embryo 

 CCXVI, length 17 mm. (38) Embryo XXII, length 20 mm. (39) Embryo 

 XLV, length 20 mm. (40) Embryo LXXXIV, length 50 mm. (41) Embryo 

 XLIV, length 70 mm. (42) Embryo XXIII, length 70 mm. 



Tlie models from ivliich the illustrations in this article were drawn 

 have been reproduced hy Dr. B. E. Dahlgren at the American Museum 

 of Natural History, New York, N. Y., and arrangements may he made 

 for securing copies hy applying to the Director of the Museum. 



