DESCRIPTION OF PLATES VI— IX— continued. 



Fig. 3. — A surface view of a blastodermic vesicle at a stage before the forma- 

 tion of the secondary cavity between the inner mass and outer layer. The 

 dark spot represents the inner mass attached to the wall of the now much 

 enlarged vesicle. Diameter of whole vesicle "31 mm., and that of the inner 

 mass 'Oi mm. ( x 39 times.) 



Fig. 4. — A surface view of the inner mass of the ovum represented in 

 figure 3 more highly magnified. Its nuclei appear smaller than those of the outer 

 layer, but owing to its thickness can only be faintly seen, (x 265 times.) 



Fig. 18 is a section through this area. 



Fig. 5. — A surface view of a blastodermic vesicle at a considerably later 

 stage ; the secondary cavity is present and is represented by the light space in 

 the centre of the inner mass. Diameter of vesicle is '9 mm., that of inner 

 mass '15 by "IG mm. ( X 39 times.) 



Fig. 24 is a section tlirougii this area. 



Fig. 6. — A blastodermic vesicle of the same stage as that represented in 

 fig. 5 ; the wall of the vesicle (o. I.) has, however, become separated from the 

 zona (z.) and, having collapsed, is more distinctly seen. (Silver preparation.) 

 The diameter of the vesicle is "9 mm. and that of the inner mass 'IS mm. 

 (x about 39 times.) 



Fig. 7. — A surface view of an inner mass of the same stage ; the secondary 

 cavity is here seen to be placed asymetrically, and to be in the form of a 

 crescent. Compare the section of this embryo in fig. 25. The diameter of 

 the inner mass is "15 by '16 mm. ( X 146 times.) 



Fig. 8. — View of a blastodermic vesicle soon after the obliteration of the 

 secondary cavity. The wall of the vesicle at this age is exceedingly thin and 

 the zona so much attenuated, that upon opening the uterus and turning back 

 its sides, the vesicle falls into the elongated shape here represented. The 

 papillae are processes of the wall of the vesicle, and project into the widely 

 open mouths of the uterine glands at this stage. Compare figures 28 and 29. 

 The embryonic area is drawn slightly too much elongated. Diameter of the 

 vesicle 1*45 by •63 mm., and that of the area "25 by -IS mm. (x 27^ 

 times.) 



Fig. 9. — Another embryo from the same uterus, the area seen in profile. 

 Diameter of vesicle 1"37 by -65 mm. (x 27^ times.) 



Fig. 10. — A surface view of an embryonic area immediately prior to the 

 formation of the primitive streak, formed of two layers throughout. In 

 section, see fig. 30. Diameter of area "43 by "35 mm. ( x 49 times). 



Fig. 11. — Surface view of an embryonic area in which the primitive streak 

 and groove are present. The former extends nearly half way along the area. 

 The region in front of the primitive streak is shaded lighter than the remainder 



