262 MICHAEL F. GUYER. 



PLATE IV. 



Figs. 100 to 117 are from embryonic ovarian or female somatic tissue, from 

 sections; 118, 119 from sections of adult testes; 120 to 132, from smears. Magni- 

 fication approximately 2,000 diameters. 



FIG. 100. Polar view, metaphase in primordial ovum of ten-day chick, showing 

 a single curved chromosome. 



FIG. 101, 102. Polar view, metaphases from region of gonad in five-day chick. 



FIG. 103. Showing curved element in nephridial tissue of ten-day female 

 embryo. 



FIG. 104. Metaphase of a dividing cell in the nephridial tubule of a ten-day 

 female embryo; the single curved element lies at one edge of the equatorial plate; 

 the long axis of the spindle lies across the short axis of the cell. 



FIGS. 105-108. Side views of metaphases in the germinal tissues of ten-day 

 female embryos, each showing a single curved chromosome. 



FIG. 109. Polar view, metaphase in nephridial tissue of ten-day female embryo. 



FIG. no. Division figure from germinal tissue of ten-day female embryo 

 showing the curved element as a much lighter stained body than the autosomes. 



FIG. in. Early anaphase in a cell from the germinal tissue of ten-day female 

 embryo showing the curved element just divided. 



FIG. 112. A stage a little later than that shown in in; from nephridial tubule 

 of same embryo. 



FIG. 113. Curved element in metaphase, nephridial tubule of thirteen-day 

 chick. 



FIGS. 114, 115, 116. Side view of division figures from ovarian tissue of thirteen- 

 day embryo, each showing a single, long, special chromosome. In 115 the chromo- 

 some was much lighter in color than the other chromosomes. 



FIG. 117. Side view of division figure in a cell from the nephridial tubule of 

 a thirteen-day female embryo; the curved element has divided. 



FIG. 118. Nuclei of spermatogonia as seen in thin sections from the testis of 

 an adult fowl. Two elongate nucleolar-like bodies are to be seen in each. The 

 urved nature of these bodies suggests that they may be the same as the two 

 curved elements which appear at division time. 



FIG. 119. Nucleus of late spermatogonium or early spermatocyte showing 

 two nucleoli and general granular appearance. 



FIGS. 1 20, 121. Nuclear phases of the early growth period of primary spermato- 

 cytes. 



FIG. 122. Nucleus showing synizesis in a primary spermatocyte. 



FIG. 123. Post-synizetic stage; two elongated, nucleolar-like bodies are 

 present. 



FIG. 124. Nucleus showing heavy spireme which immediately precedes the 

 formation of chromosomes in primary spermatocytes. 



FIGS. 125-132. Nuclei showing transition stages between the breaking up 

 of the spireme and the formation of the chromosomes in primary spermatccytes. 

 The difference in size of the nuclei is probably due to different degrees of flattening 

 in making the smear rather than to an actual difference. Fig. 132 shows various 

 tetrad-like groups. 



