266 MICHAEL F. GUYER. 



PLATE VI. 



All drawings are from smear. Figs. 168, 169, 171 are from Plymouth Rock, 

 Figs. 153, 163-166, 170 and 174 from Langshan, and the remaining figures except 

 160 are from Rhode Island Red fowls. Magnification approximately 2,000 diam- 

 eters. 



FIGS. 153-158. Polar views of equatorial plate stages showing various rela- 

 tions of the special curved chromosome to the other chromosomes. 



FIG. 159. Side view showing same. 



FIG. 160. Polar view of an equatorial plate stage in a primary spermatocyte 

 of the guinea-fowl. In the guinea the accessory chromosome is characteristically 

 comma-shaped. 



FIG. 161. Equatorial plate stage in a secondary spermatocyte, showing five 

 chromosomes. 



FIG. 162. A five-chromosome and a four-chromosome group lying in a common 

 mass of cytoplasm each ready for division as a separate nucleus. 



FIG. 163. Side view of an equatorial plate stage in a secondary spermatocyte, 

 showing five chromosomes, one of which is the curved chromosome received from 

 the primary spermatocyte. 



FIG. 164. Telophase of a dividing primary spermatocyte showing secondary 

 pairing of the daughter chromosomes in preparation for the next division. The 

 eight ordinary chromosomes at each end pair to form four: the extra curved chromo- 

 some remains unpaired. 



FIGS. 165, 166. Side views of metaphases in secondary spermatocytes showing 

 curved chromosomes at one edge. 



FIGS. 167-174. Various anaphase stages in the division of the five-chromo- 

 somed secondary spermatocytes. In 168 and 172 the double nature of the auto- 

 somes is indicated by their bipartite appearance. The lagging in division of the 

 fifth chromosome is indicated in 167, 168, 172-174. 



