Conti-, towards tbe Embryology and Anatomy of Polistes pallipes. 193 



change takes place in both the arrangemeut of the cells and in the 

 structure of their nuclei. The epithelial like arrangement entirelj 

 disappears and the cells become irregularly scattered throughout the 

 tubule. The ovoid nuclei are much less abnndant, and larger and 

 more rounded ones take their place. In the upper part of the middle 

 portion we find that the first differentiation , as in the younger 

 stage, can be seen where the oöcyte nuclei are slightly different 

 from those of the primitive nurse-cells (Fig. 39 a and h). When these 

 nuclei are compared with those we find in the same region of the 

 last stage (Fig. 28 and 29), the similarity is at once apparent. Near 

 this same region (Fig. 37, positions 40 and 41) we find exactly the 

 same changes taking place in the nuclei of the primitive nurse-cells, 

 that we found in an earlier stage. They obtain a definite spherical 

 form, the Strands of achromatin assume a net-like arrangement, and 

 a yolk-nucleus appears in many of the cells (Fig. 40). The chromatin 

 granules increase in size (Fig. 41) and around each one a small 

 achromatin mass is formed. Further down in the tubule, the clearer 

 nuclei we have already mentioned, are present (Fig. 42), and they 

 show here, as in the earlier stages, a Variation in size and in the 

 amount of contained chromatin. Within the proximal part of this 

 median portion a few nuclei with chromosomes were seen. 



In this ovary we find that the nurse-cell nuclei are, in 

 corresponding parts, similar to those we found in the last stage. 

 In the oöcyte nuclei we notice that very important changes have 

 taken place and that they are no longer the same from all parts of the 

 tubule in which they are found. Distal in the median portion of the 

 tubule, we still find cells with rather large, irregulär nuclei (Fig. 39 «), 

 which are similar in structure to the oöcyte nuclei of the last two 

 stages (Figs. 25 and 29 a); when however we come tothe older stages 

 we notice that there has been a decided change. At a position in 

 the tubule which we have represented (Fig. 37, point 43) we find a 

 few nuclei which, from the size of both cell and nucleus, we know 

 to be those of oöcytes: they show a few beut, beaded, rod-like 

 chromosomes and also some achromatin matter (Fig. 43). The nature 

 of this latter substance was hard to determine, it formed irregulär 

 Strands which were not clear. Both in the oöcytes and in the primitive 

 nurse-cells, the chromosome stage was less abundant than anj of the 

 other forms. 



In the oöcytes the chromosomes next lengthen to threads in which 

 a beaded structure is easily seen. Such nuclei, (Fig. 44), lie proximal 



