236 Proceedings of the Boyal Physical Society. 



times right into* the nucleus proper, in which the chromatin 

 may show traces of a spiral arrangement (Fig. 11). Nuclei, 

 with chromatin forming a quite definite spiral band, are also 

 found in individuals which do not show the band in the 

 pre-nuclear part of the body (Fig. 12). Cross bars (Fig. 7) are 

 often found instead of the spiral band ; these strongly suggest 

 that they have been formed by the nipping across of the 

 spiral. The bars (Figs. 5, 8, 9) now apparently become con- 

 nected with the central line, and presently it is found that 

 the red staining reaction begins to be lost — the time at which 

 this happens seems to vary. They are soon reduced to little 

 concentrations along the central line, with faint bars going 

 out at right angles ; the bars may then disappear, leaving 

 only the violet-blue thickenings. The spiral band, though 

 not by any means rare, is still not a very frequent appear- 

 ance, and the same may be said of the red staining cross 

 bars, but the two last stages are quite commonly seen ; the 

 central line, as I have before mentioned, occurs in a very 

 large proportion of individuals. I am unable to suggest 

 what is the functional importance of the spiral band. Appear- 

 ances such as those just described are usually quite absent 

 from the post-nuclear part, but indistinct thickenings of the 

 central line and stray red staining bars are occasionally seen : 

 these are, however, rare exceptions, and may be regarded 

 possibly as vestigial in character. 



The band, in my opinion, is to be interpreted as the 

 remnant of a primitive spiral running the whole length of 

 the animal, and representing the chromatic part of the 

 primitive nuclear apparatus, the central line representing the 

 primitive karyosome. The nucleus, as now found in the 

 majority of the trypanosomes, would be, on this view, a con- 

 centration of the central portion of the primary elongated 

 apparatus. This view is the more probable, as the primitive 

 condition of a spiral breaking up into cross bars is not 

 infrequently found in the somatic nucleus of the trypano- 

 somes I examined (Figs. 10, 12). It is an interesting ques- 

 tion as to whether there may not be a possible phylogenetic 

 connection between this primitive spiral and the spireme 

 of much higher forms. 



