The Early Development of the Pigeon's Egg. 



Ipb 



2pb 



^U 



taken from the oviduct at 



(?$ CO nP 



—Transverse section of a pigeon's egg 



m., about 3l^ hours after fertilization. Reference marks are the 



for Fig. 3. Leitz, 4/2. Tube length, 140 mm. 



Fig. 3. — Diagram of Fig. 2. A central transverse section of pigeon's 

 egg obtained at 11 :?>0 p. m., SV2 hours after fertilization. The nuclei are 

 reconstructed from seven successive sections. 



1 pb, first polar body; 2 pb, second polar body; ^, male pronucleus; 

 9 , female pronucleus ; sn, supernumerary sperm nuclei ; mp, marginal peri- 

 blast ; cp., central periblast ; wy, white yolk ; n P, nucleus of Pander. 



2 cp wy 



Fig. 4. — Transverse section througli about the center of the blastoderm 

 of a pigeon's egg obtained at 2 :(X) a. m., about six hours after fertilization. 

 The same egg is shown in Chart II. n, nucleus of one of the blastomeres. 

 mp, marginal periblast, cp, central periblast, wy, white yolk, ac, a cell 

 in the accessory cleavage. 1, a sperm nucleus in the marginal periblast, and 

 2, a sperm nucleus in the central periblast. Leitz, 4/2. Tube length, 140 mm. 





Fig. 5. — Transverse section of the pigeon egg whose surface view is 

 shown in Fig. 37. a, b, c, d, cells of primary cleavage. 1, accessory cleavage. 

 2, sperm nuclei. 



