542 A. C. WALTON 



threads correspond to the ones described by Marcus ('06) for 

 his A. canis, and by Lukjanow ('89) for A. marginata. At the 

 same time the plasmosome may show signs of degeneration. It 

 may now (fig. 17) break up into a few small, deeply staining 

 granules (Heidenhain's iron-haematoxylin) , surrounded by a 

 more faintly staining ground substance, and then shortly dis- 

 appear; or it may persist as a compact body until the final re- 

 formation of the chromosomes before it entirely disappears. 



The concentrated mass of stained material, consisting of 

 chromatin and linin, begins to show a differentiated appearance 

 in the majority of cells before the network entirely disappears 

 (fig. 17), thus indicating that the linin network, as well as the 

 chromatin, had been involved in the condensation process, and 

 that it had not become invisible merely by becoming diffused 

 generally throughout the nucleus. This differentiation proceeds 

 rapidly (fig. 18), dark bodies of chromatic material being easily 

 distinguishable against the less deeply staining linin when iron- 

 haematoxylin is used. With safranin, followed by licht-grlin, 

 the contrast is sharp between the reddish chromatic bodies and 

 the greenish substratum of linin. The karyosomes thus differ- 

 entiated are thirty-six in number, the diploid number character- 

 istic of the sex cells of the female. The plasmosome is in some 

 cases included in the condensation mass as a definite body, and 

 as such is again released upon the dissolution of the mass ; but in 

 other cases it is not so included. 



The linin ground-work becomes rapidly diffused, and «iis- 

 appears, leaving the karyosomes lying free in the karyoplasm. 

 At first closely grouped, the karyosomes soon spread throughout 

 the peripheral region of the nucleus (fig. 19) and then gradually 

 a few of them take up a more central position. These bodies 

 are ellipsoidal, not as yet showing the definite constriction per- 

 pendicular to the long axis that was noted in the chromosomes 

 formed in the early prophasic nuclei (fig. 7) after the last oogonial 

 division. This method of the formation of the chromosomes 

 differs markedly from that ordinarily described for the Ascari- 

 dae. It corresponds, however, exactly with that of the forma- 

 tion of the diploid chromosomes in the primary spermatocytes 



