EXPLANATION OF FIGURES. 



319 



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 KoUiker (magnified, about 100 times) ; 

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



h^ horn-plate ; *mr, spinal tube ; n.ng, primitive kidney duct ; un, pri- 

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

 plate ; uw, primitive vertebral plate {wh, membranous formation of the 

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

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

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

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

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

 secondary aorta; vc, piincipal veins; 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 



