L. DONCASTER 197 



end of the egg-tube, but are not, I believe, true oocytes. Among them, 

 fewer in number, are somewhat larger nuclei, which always lie in the 

 middle of the egg-tube, either surrounded by those of the type just 

 described, or extending further down the egg-tube than the latter. 

 I believe these larger nuclei are those which will give rise to the 

 egg-nuclei ; the kind described just previously probably belong to 

 the cells of the egg-follicles or the nutritive cells. The large nuclei, 

 which appear to be those of the true oocytes, contain a very large 

 nucleolus and interlaced chromatin threads, which have not contracted 

 into short loops. Their number is difficult to count, but appears to 

 be the haploid number (27) rather than the diploid (o-i). The nucleolus 

 appears to consist chiefly of chromatin ; it is either double or divided 

 into two separate parts, and each part consists of a number of masses 

 of chromatin apparently embedded in achromatic material, which, 

 however, is not very easy to demonstrate. The irregularity of the 

 chromatin masses composing the two parts of the nucleolus makes it 

 difficult to determine whether the two parts are equal or unequal ; 

 in some nuclei no difference in size is visible, in others one mass is 

 certainly larger than the other. The nucleolus appears rather as a 

 store of chromatin than as a definite chromosome. 



In addition to the two classes of cells described in the lower region 

 of the ovary-tube, there are cells of varying size with many scattered 

 chromatin granules in the nucleus. These are occasionally found in 

 division, and show about 56 chromosomes ; if the cells described above 

 give rise to the nutritive cells and true oocytes, these last are probably 

 the follicle-cells. 



In conclusion, then, it appears that Abraxas, like Pieris, has an 

 even number of oogonial chromosomes, with no evidence of an un- 

 equal pair. In the early stages of the meiotic phase two of these 

 give rise to a double chromatin-nucleolus, and the remainder undergo 

 synizesis, from which they emerge in the haploid (reduced) number 

 of chromatin threads. In cells which probably do not become true 

 oocytes, these threads then become contracted into short loops, which 

 break at the bend and give rise to the reduced number of pairs of 

 chromosomes. The members of the pairs may then separate. In the 

 true oocytes the bivalent threads persist to the latest stage observed — 

 possibly till the prophase of the polar divisions. The halves of the 

 chromatin-nucleolus, though not always identical in size, do not show 

 any constant differences which would justify the assumption that it 

 may be regarded as an unequally paired heterochromosome. The 



