358 EICHARD ASSHBTON. 



Fig. 7 (Sus 25, No. 6). — Embryo of pig in morula stage. Found in uterus. 

 Drawn after the specimen had been treated with chromic acid. Age 6 days. 

 X 380. 



Fig. 8 (Sus 25, No. 7). — Embryo of pig. Morula stage probably not quite 

 attained. Age 6 days, x 380. 



Fig. 9 (Sus 2G, No. 13). — Embryo of pig. Advanced blastodermic vesicle 

 stage. Age 5 days, x 380. 



Fig. 10 (Sus 28, No. 2). — Embryo of pig. The blastodermic vesicle is now 

 a large thin-walled sac of irregular shape. This is double-layered ; aud the em- 

 bryonal area is a circular or sometimes slightly oval patch upon one side of it. 

 Age 10 days 2J hours, x 20. 



Fig. 11 (Sus 33, No. 1). — Embryo of pig. The blastodermic vesicle is 

 thrown into many folds. Age 8 days. X 20. 



Fig. 12 (Sus 28, Nos. 5, 3). — The embryonal areas of two specimens 

 showing the pieces of trophoblast, T. R,, lying upon the disc of true epiblast. 

 The specimen from wliicli the smaller embryonal area was taken measured 

 about 3 mm. in length. The embryonal area itself measured "215 X '190 mm. 

 The specimen from which the larger figure (b) was taken measured 3*5 mm. 

 by 2"9i mm., and the embryonal area was about "22 mm. in diameter. The 

 two figures were drawn with the camera lucida, but under different magnifying 

 power. 



PLATE 26. 



All the figures on this plate are camera drawings of sections of embryos of tlie 

 pig. The magnification in every case is 380 times. 



Fig. 13 (Sus 23, No. 3).— Age 6 days 3 hours. 



Fig. 14 (Sus 23, No. 1).— Age 6 days 3 hours. 



I'iG. 15 (Sus 25, No. 10).— Age 6 days. 



Fig. 16 (Sus 29, No. 1).— Age 5 days. 



Fig. 17 (Sus 19, No. 2).— Age 5 days 3 hours. 



Fig. 18 (Sus 26, No. 2).— Age 5 days. 



Fig. 19 (Sus 31, No. 8).— Age 4| days. 



Fig. 20 (Sus 27, No. 1).— Age 5 days. 



In all the foregoing the zona radiata is present, but after this point it has 

 ruptured and disappeared. 



Fig. 21 (Sus 32, No. 4).— Age 7 days. 



Fig. 22 (Sus 14, No. 6).— Age 7^ days. 



Fig. 23 (Sus 14, No. 6).— Age 7i days. 



Fig. 24 (Sus 33, No, 6).— Age 7 days. 



