STCDIBS IN MAMMALLiN EMBRYOLOGY. 561 



Figs. 70 — 77. — Eight sections through part of the embryonic shield of 

 Fig. 63. Lettering as above. 



Fig. 70.— Mus. Utr. Cat. n°- Sorex 45 b, 2 r. +§ s. 

 Fig. 71.— „ „ „ 25 s. 



Fig. 72.— „ „ „ 3 r, 3 s. 



Fig. 73.— „ „ „ 5*. 



Fig. 74.— „ „ „ 7 s. 



Fig. 75.- „ „ „ 9*. 



Fig. 76.— „ „ „ lis. 



Fig. 77.— „ „ „ 17 5. 



Fig. 78. — Part of a section through an embryonic shield not here figured. 

 Here, again, there is an unmistakable rudiment {c.) of a canal in the proto- 

 chordal wedge. 



Mus. Utr. Cat. u""- Sorex 45 a, 4 r. 2.2, s. 



PLATE XLI. 



Figs. 79 — 81. — Three surface views of three embryos from the same uterus 

 (No. 42). They were obtained in the same way as those of the foregoing 

 plates, pp., 2'^; gr. as in Figs. 62 — 64. Ccel. Regions of the coelom. 

 {jper. : in Fig. 80 first indication of pericardial ccelom, in transverse sections 

 in Fig. 88.) 



Fig. 82. — The uterus, No. 42, drawn from the spirit specimens (natural 

 size). 



Figs. 83 — 87. — Five sections through the embryonic shield of Fig. 79. 

 The sections are oblique, i. e. asymmetrical. This brings out all the more 

 clearly (especially in Fig. 87) the slight but still marked differences between 

 the niesoblast that more particularly belongs to the protochordal plate {ines. 

 pp.), that which is continuous with the protochordal wedge {ines. pw.), and 

 that which belongs to the region of the gastrula-ridge {mes. gr.). Lettering 

 as before, gr. and gg. The front end of gastrula-ridge and gastrula-groove 

 as seen in oblique sections. (In Figs. 85 and 86, and. also in Fig. 90, there 

 are rudiments of a protochordal canal inside the protochordal wedge.) 



Fig. 83.— Mus. Utr. Cat. n°- Sorex 42 c, 3 r. 6 d. 



Fig. 84.— „ „ „ \Qd. 



Fig. 85.— „ „ „ 12 c^. 



Fig. 86.— „ „ „ 13 rf. 



Fig. 87.— „ „ „ ISd. 



Figs. 88 and 91. — Two sections as indicated in Fig. 80. 

 Fig. 88.— Mus. Utr. Cat. n°- Sorex 42 e, 3 n 6 s. 

 Fig. 91.— „ „ „ 19 J. 



Figs. 89 and 90. — Idem for Fig. 81. Lettering as above. 

 Fig. 89.— Mus. Utr. Cat. n°- Sorex 42 b, 4 r. 27 s. 

 Fig. 90.— „ „ „ 22 s. 



