360 SYDNEY J. HICKSON. 



Fig. 3. Stage B. — The niegaiiuclei have become spiudle-sliaped and arc 

 slif^litly enlarged. The micronuclei (t.liree in each individual) are considerably 

 enlarged, the chromatin forming a loose meshwork. Section No. 139. 



In this and the following figures details of the arms are omitted. 



Fig. 4, Stage B (later). — The micronuclei now show chromosomes arranged 

 in equatorial planes and linin fibrils running through them to the poles. In 

 this preparation only two micronuclei can be seen in each individual. 

 Sections No. 129. 



Fig. 5. Stage B (close). — The micronuclei are in later stages of their 

 mitosis. In the individual ou ihe right the chromosomes of the micronuclei 

 have separated into two parties travelling toward the poles. In the individuals 

 on the left the chromosomes have reached the poles and fused into a compact 

 mass. Whole mount, No. 14. 



Fig. 6. Stage C. — There are now six micronuclei in each individual, and the 

 undissolved remnants of someof tiie spindles (Sp.) may be seen in the cytoplasm. 

 The meganuclei have been omitted from the drawings to render the positions 

 of the nuclei clear. Section No. 139. 



Fig. 7. Stage D. — Five of the micronuclei in each individual are now under- 

 going degeneration, but one in each (m.c.) travels down the conjugative 

 process and approaciies the membrane of separation. The meganucleus is 

 omitted in the figure from the individual on the right. Sections No. 126. 



Fig. 8. Stage D. — The conjugative micronuclei (mc, mc.) are now dividing 

 by mitosis in the conjugative process of each individual. Sections No. 134. 



Fig. 9. Stage E. — Tiie conjugative micronuclei have now divided into two 

 separate nuclei. — the " germ nuclei." Sections No. 138. 



Fig. 10. Stage F. — The germ nuclei of the two individuals have now fused 

 or are fusing (upper one). Sections No. 140. 



Fig. 11. Stage G. — The cleavage nuclei (S.m.) formed by the fusion of the 

 halves of the conjugative nucleus in the last stage now travel towards the 

 centre of each individual and again show mitosis. During the preceding 

 stages the meganuclei have been gradually enlarging and liave now reached a 

 considerable size. Degenerate remnants of the other micronuclei may still be 

 seen in the cytoplasm. Sections No. 141. 



Fig. 12. Stage H. — Tiie segmentation nuclei having divided once more 

 show mitosis. Sections No. 107. 



For illustrations of Stage J see Plate 17, figs. 1, 7, 8. 



Fig. 13. Stage K.^— The segmentation nuclei have now divided into four 

 iiuclei in each individual, three of which become reduced in size and the 

 chromatin concentrated into a single granule, and one j.in each becomes 

 enlarged to form the new meganucleus (n. M.). The old meganucleus is 

 beginning to disintegrate. Sections No. 25. 



