The cellnlar elements of the Ovaiy of Platyphylax designatiis Walk. 221 



the Center of a tubule, we can trace in it nearly tlie entire histoiy 

 of the cells, from tlieir first cliange from an undifferentiated cell, to 

 the stage when they have the paired chromosomes as possessed by 

 all young oöcytes and nurse-cells. All these last mentioned, here 

 the oldest, cells have similar nuclei, and it has been impossible, in 

 this tubule, to distinguish between oöcyte and nurse-cell; at a little 

 later stage this can be done by the size of the former. We shall 

 see later that when the group of oöcyte and accompanying nurse-cells 

 are first formed they show no difference in miclear structure. 



Distally in this tubule (Fig. Ib a, h and c) we find the same 

 nuclear structure present that we found in the younger ovary. Only 

 a few undifferentiated cells (Fig. 15 a) are present, and these are, 

 with few exceptions, found on the margin. In most of the cells at 

 this end the nucleus shows a number of large chromatin granules, 

 and this stage is here much more prevalent than any other. These 

 are of exactly the same structure as we found in ovary A (Figs. 3, 

 4 and 5 ö); each has an achromatin nucleolus and a number of large, 

 rather Square , chromatin granules (Fig. 16 h) around each of which 

 lies a small mass of achromatin. The next stage, that in which the 

 achromatin Strands become prominent, is found scattered in among 

 these last and also lying proximal to them (Fig. 15 c). Düring this 

 change many of the Strands show a beaded structure even before the 

 chromatin granules have decreased very much in size (Fig. 16 c). 

 We find that, as the chromatin granules disappear, the beaded Strands 

 become more and more prominent until, when the spireme-threads 

 have formed, there is nothing left of the former (Fig. 20). A some- 

 what similar spireme-thread stage is figured by Grünberg (12) for 

 Bomhyx mori and he says that all »Keimzellen« nuclei pass through 

 it. He describes the thread as at one time beaded. A beaded spireme^ 

 thread has been found by Stschelkaxovzew (35) for Apliis rosae. 



At about the middle of the tubule (Fig. 15 c) we find a number 

 of nuclei in synapsis; these are at once distinguished by their 

 structure and their staining darker than in the last stage. Neither 

 Paülcke (28) for Apis, nor Grünberg (12) for Pieris, could find 

 any cell boundaries during synapsis as we find them here in Platy- 

 phylax. The nucleolus is still present but generally hidden, it does 

 not always lie at the pole towards which the threads have con- 

 tracted. It is rather difficult to distinguish any difinite arrangement 

 of the threads ; most of them lie closely packed together and do not 

 show such great regularity as Giardina (8 and 9) has figured for 



Zeitschrift f. wissensch. Zoologie, LXXXYI. Bd. 15 



