EXPLANATION OF FIGURES. 



Fig. 98. 



FIGS. 95-98. Transverse sections through embryo Chick: Fig. 95, the 

 second day of incubation ; Fig. 96, the third ; Fig. 97, the fourth , and Fig. 

 98, the fifth. Figures 95-97 are after Kolliker (magnified about 100 times) ; 

 Fig. 98, after Kemak (magnified about 20 times). 



h, horn-plate ; Vnr, spinal tube ; ung, primitive kidney duct ; wn, pri- 

 mitive kidney vesicle ; hp, skin-fibrous layer ; m = mu = mp, muscle- 

 plate ; ww, primitive vertebral plate (ivh, membranous formation of the 

 vertebral body ; wb, of the vertebral arch ; wq, of the rib, or transverse 

 apophysis) ; uwh, primitive vertebral cavity ; ch, spinal axis, or aoto- 

 chord ; sh, notochord-sheath ; bh, ventral wall; g, posterior; v, anterior 

 nerve roots of the spinal marrow ; a = of = am, amnion-fold ; p, body- 

 cavity, or ccelom ; df, intestinal-fibrous layer ; ao, primitive aortas ; sa, 

 secondary aorta ; vc, principal reins ; d dd, intestinal-glandular layer ; 

 dr, intestinal groove. In Fig. 95, the greater part of the right half of the 

 cross-section is omitted, and in Fig. 96 the greater part of the left half. 

 Only a small part of the wall of the yelk-sac, the remnant of the germ- 

 vesicle, which lies below, is shown. 



especially to those who are not at all familiar with the 



