Blacksian. — Spermatogenesis of Seolopendra. 



PLATE 8. 



All figures of Plates 8 and 9 are reproductions of photomicrographs made by the 

 author. Photographs 122-165, 1(39, and 178 were made with the camera vertical, 

 using daylight as the source of illumination. The Foot and Strobed (:01) method 

 of focusing was used. Photographs 104, 105, 108, 170, and 173 were made with the 

 camera horizontal, using a Nernst light of about 50-candle power as the source of 

 illumination. In Figures 133, 140, 146, 148, and 154 the centrosomes have been 

 made more prominent by retouching the negative. 



Figure 122 is magnified 130 diataeters ; Figure 132, G56 diameters ; Figures 134, 136, 

 13y, and 140, 520 diameters; all others, 800 diameters. 



Fjg. 122. Cross section of follicle of the testis of Seolopendra heros, showing the 

 general arrangement of the various generations of cells. X 130. 



Fig. 123. Spermatogonia in the "resting stage," the same as that of Figure 2. 



Fig. 124. Early prophase of spermatogonium. Two nuclei lie one above the other 

 and so close to each other that they appear in the photograph as one. 



Fig. 125. Metaphase of spermatogonium. 



Fig. 12t3. Telophases of last spermatogonia, showing the massing of the chromatin 

 dining synapsis. 



Fig. 127. Early stage of first spermatocyte at the time when the chromatin is col- 

 lecting to form the karyosphere. 



Fig. 128. Portions of the two spermatocytes derived from one spermatogonium. 

 The interzonal filaments still persist. 



Fig. 129. 'Vesicle" stage showing a karyosphere in which the chromatin is 

 aggregated into irregular masses. 



Fig. 130. Typical " vesicle " stage of the large spermatocyte. 



Fig. 131. Nucleus of same stage. The section has passed through one side of the 

 karyosphere, showing the spireme character of the chromatin. 



Fig. 132. Nucleus of first spermatocyte of Seolopendra subspinipes, showing the 

 character of the karyosphere in this species. 



Fig. 133. Portion of the spermatocyte in the "vesicle" stage. The two centro- 

 somes are in the mass of archoplasm at the right of the nucleus. 



Fig. 134. Late prophase. The chromatin segments have become condensed into 

 homogeneous chromosomes. The centrosomes lie at the two poles of 

 the nucleus, only one being shown in this section. 



Fig. 135. From the same cell that is shown in the preceding figure. The second 

 centrosome is visible in this section. 



Figs. 136, 138. Mid prophase. A number of chromatin segments have arisen from 

 the karyosphere, which has decreased in size. 



Fig. 137. Very early prophase of first spermatocyte. The masses of archoplasm 

 around the nucleus have disappeared. The centrosomes have migrated 

 to the nucleus and begun their migration along its membrane. One is 

 shown in the photograph, while the other is out of focus. 



Fig. 139. Abnormal spermatocyte in " vesicle "stage. In such cells the chromatic 

 material is much more plentiful than in normal cells and there may be 

 from 2 to 10 karyospheres. 



Fig. 140. Centrosome, centrosphere, and aster as seen in the early metaphase. 



