26O MICHAEL F. GUYER. 



PLATE III 



All drawings on this and the following plates are the work of Miss Hattie J. 

 Wakeman. They were made with the aid of a camera lucida. Unless otherwise 

 specified their magnification is approximately 2,000 diameters. All on this plate 

 are from sections of male tissues. Figs. 72, 76, 81, 86, 87 and 95 are from the 

 testes of chick embryos. All other figures except 79 are from cells in nephridial 

 tubules of embryos. 



FIGS. 70-78. Polar views of division stages showing the two curved elements 

 in various germinal (72, 76) and somatic cells of embryo chicks. In some a number 

 of the autosomes have been cut away, in others all or most of the chromosomes 

 are present. Fig. 76 is from a thirteen-day embryo, the others from ten-day 

 embryos. 



FIG. 79. Spermatogonium of adult fowl showing two curved chromosomes. 

 The remaining chromosomal mass could not be resolved into individual elements. 



FIGS. 80-85. See remarks under Figs. 70-78. Fig. 81 is from a fifteen-day 

 embryo, the others from ten-day embryos. 



FIG. 86. Side view of metaphase in primitive spermatogonial cell of ten-day 

 chick embryo. Two relatively huge curved elements are present at each edge of 

 the equatorial plate. 



FIG. 87. The same kind of cell and the same condition as in 86. 



FIGS. 88-96. Comment same as for 70-78. Figs. 88, 94, 96, from nephridial 

 cells of ten-day embryos; Fig. 95 from testis of thirteen-day embryo. 



FIG. 97. Anaphase in cell of nephridial tubule; each of the two curved elements 

 has divided. 



FIG. 98. A stage in a nephridial cell comparable to Fig. 86 of a primordial 

 germ-cell. 



FIG. 99. Probably a stage comparable to that shown in Fig. 97, only the 

 curved elements from one side have been cut away. 



