JOURNAL OF MICROSCOPICAL SCIENCE. 



EXPLANATION OF PLATE XII, 



Illustrating Mr. Kidd's paper on Some Points in the 

 Early Development of the Hen's Egg. 



In all cases g = germ ; s = subgermiual layer; y ^ yolk. 



Fig-. 1. — Chromic-acid preparation. Incubated for fourteen hours, g is 

 seen to be divided into two portions, separated by a thickened mass of s. 

 Hartnack 2 — 4 in. tube. 



Fig. 2. — Osmic-acid preparation. Incubated for twelve hours. Resem- 

 bles 1, but segmentation here is less advanced. Hartnack 2 — 4 in. tube. 



Fig. 3. — Osmic-acid preparation. Incubated for twelve hours. Seg- 

 mentation more advanced than in 1 and 2. s Absent at left-hand side, but 

 presents a wedge-shaped appearance at the right, and is divided off from 

 the subjacent yolk by a fine cleft. Hart. 2 — 4 in. tube. 



Fig. 4. — Chromic-acid preparation. Incubated for eight hours. Seg- 

 mentation less advanced. Wedge-shaped mass of s at right side contains 

 numerous nuclei. Hart. 2 — 7 in. tube. 



Fig. 5. — Chromic-acid preparation. Incubated for fourteen hours. 

 Segmentation more advanced here than in the others. Peripheral thick- 

 enings of 5 well marked at both ends. Hart. 2 — 4 in. tube. 



Fig. 6. — Osmic-acid preparation. Incubated for twelve hours. The 

 germ is seen to be in direct continuity with the subgerminal layer at one 

 place. Both ff and s richly nucleated. Peripheral thickenings of s. Well 

 marked. Hart. 2 — 7 in. tube. 



Fig. 7. — Chromic-acid preparation of a normal uniucubated egg showing 

 only the floor of the subgerminal cavity with a few large cells Tying on it. 

 The subgerminal layer here also is seen to be nucleated. Hart. 2 — 7 

 in. tube. 



