Contr. towai'ds the Embiyology iiud Aiiatomy of Polistes pallipes. 187 



rounding-, of the cells. After this change the nuclei are for some 

 time very similar in structure. A short distance proximal to this point 

 some of the cells lie in groups; there is a central part, common to 

 all, which is darker than the rest, and this darkened portion extends 

 a short distance up into each cell. Often the connection between this 

 portion, and that part protruding into the cell, is, on account of the 

 Position of the cell, lost, and the cell then appears to have an irregulär 

 or round, darkened body in its attached end (Fig. 16, lower cell). 



Within the central part of the tubule (Fig. 13 ov) some variations 

 in nuclear structure are noticed. At the distal end the nuclei are 

 all nearly alike, very similar to what we have figured (Fig. 23). 

 A little proximal to this the only change noticeable is an increase 

 in size of the chromatin granules. Such nuclei (Fig. 16) may be found 

 at any place in the proximal two-thirds of the median portion of 

 the tubule. Scattered through this part are some slightly larger, 

 irregulär cells, with one, seldom two, large nucleoles, and having the 

 small chromatin granules nearly all peripheral in position (Fig. 15). 

 These we believe to be young oöcytes, but they nowhere, at this age, 

 show any of the changes which we shall find at later stages. 

 Grüxberg (12) has noticed for Pieris^ that early, the nucleus of the 

 oöeyte and of the nurse cells, were to be distinguished by the 

 dilferent distribution of the chromatin: all nuclei of the »Keimzellen« 

 he found had a spireme thread stage. He could, in half grown 

 larvae, distinguish between the three kinds of cells. Blochmann (3) 

 distinguished the young oöcytes by their great size and their darker 

 staining cytoplasm, Korschelt (18), the young oöcytes, by their 

 lighter color; the earliest stages both these saw were however much 

 older than the present one. A third form of nucleus which shows 

 considerable Variation in size, is found especially in the proximal 

 half of this portion of the tubule. One of the smallest of these 

 (Fig. 17), is Seen to contain an irregulär, loose achromatin mass, in 

 which a few chromatin granules of varying size can be seen. Very 

 similar but larger nuclei are present, these differ from the small 

 ones, in having the Strands of achromatin more definite, and tlie 

 chromatin granules more numerous. All gradations between these 

 small and larger nuclei can be found. These we hold to be the 

 nuclei of primitive nurse-cells soon after division, and that they are, 

 by increase in size and amount of chromatin, assuming a structure 

 very similar to figure 16. A number of these nuclei are generally 

 found together and we shall notice them in later stages. 



