130 .1. P. HILL. 



PLATE 4. 



Fig. 38. — Photo-micrograph ( X 10) of entire blastocyst 4-5 mm. dia- 

 meter to show the junctional line (j. I.) between formative and non- 

 formative regions. From a spirit specimen. (D . viv., ^, 25 . vii . '01. 

 Picro-nit ro-osni i e . ) 



Fig. 39. — Photo-micrograph ( X al:>out 10) of an entire blastocyst, 

 4"5 mm. diameter with distinct embryonal area (emh. a.). (D. viv., 5, 

 18 . vii . '01.) 



Fig. 40. — Photo-micrograph ( x 10) of entire blastocyst aliout 5 mm. 

 diameter showing emliryonal area (emh. «.). peripheral limit of ento- 

 derm (l. ent.), and the still nnilamiuar region of the wall {tr. ect.). (D . 

 viv.,8. vi . "01.) 



Fig. 41. — Photo-mici-ograph ( X 150) of an in toto preparation of the 

 wall of a blastocyst of 3'5 mm. diameter. (D. viv., 16. 21 . vii . '01.) 



Fig. 42. — Photo-micrograph (x 150) of an in toto preparation of the 

 wall of a blastocyst of 3"25 mm. diameter, j. I. Junctional line between 

 the formative (/. a.) and non-formative (tr. ect.) regions of the wall. 

 (D. viv., 24. vii . '01.) 



Figs. 43 and 44. — Photo-niicrograx)hs ( x 150) of in toto preparations 

 of the wall of 4"5 mm. blastocyst showing the junctional line between 

 the formative (/. a.) and non-formative {tr. ect.) regions. (D. viv., 

 /3, 25 . vii . '01. Picro-niti'O-osmic and Ehrlich's hsemato.xylin ) 



Fig. 45. — Photo-micrograph ( x 150) of a corresiionding preparation 

 of the wall of a more advanced 4"5 mm. blastocyst ("99 stage), in which 

 the two regions of the wall are now clearly distinguishal)le. (D. viv., 

 8.7. '99. Picro-nitro-osmic, Ehrlich's hsematoxylin.) 



Fig. 46. — Photo-micrograph (x 150) of a corresponding preparation 

 of a slightly moi-e advanced blastocyst ("04 stage). (D. viv.. 6 . T . '04. 

 Picro-nitro-osmic, Ehilich's haimatoxylin.) 



PLATE 5. 



Fig. 47. — Photo-micrograph (x 150) of an in toto preparation of the 

 formative region of a 6 . 7 . '04 blastocyst, showing the proliferation 

 of spherical internal cells referred to in the text, p. 53. 



Fig. 48. — Photo-micrograph ( x 150) of an in toto preparation of the 

 wall of a vesicle of the same batch as that represented in fig. 39, in 

 which a small part of the junctional line between the embryonal ecto- 

 dei-m and the extra-emln-yonal {tr. ect.) is visible, the free edge of the 

 entoderm {eiit.) not having reached it. (D. viv., 5, 18 . vii . "01. Picro- 

 niti'O-osmic, Ehrlich's h*matoxylin.) 



