218 



Wm. S. Marshall, 



the gonads of the embiyo and youngest larvae contain nuclei which 

 are all similar (Henking [16]). We believe tliat in Platyphylax the 

 same would be true and that this kind of nucleus would be tbe only 

 one found in the very young larvae. These undifferentiated cells 

 (Figs. 3, 4 and 5 a) have either an oval or sperical nucleus ; in this 

 there is a Single achromatin nucleolus, a number of small chromEtin 

 granules connected by achromatin Strands. These cells and their 

 nuclei grow; the first change we notice in their structure is an in- 

 crease in the size of the chromatin granules which become very 

 prominent (Figs. 3 and 4 h). Cells with such nuclei are mostly in 

 the distal half of the tubule. The chromatin granules become in 

 many so prominent as to appear, from a surface view, to nearly fill 

 the nucleus. They are mostly peripheral in position and are nearly 

 Square in shape. The large achromatin nucleolus is present, the 

 Strands are not so npticeable but a little achromatin matter lies 

 around each chromatin granule and can be seen extending some little 

 distance from many of them. Whether the Strands really in part 

 disappear or are hidden by the large chromatin granules I am unable 

 to say. There are many nuclei with both large chromatin granules 

 and prominent achromatin Strands, but these we believe to be the 

 next stage. Such nuclei (Fig. 5 c) we find at almost any place, ex- 

 cept the proximal end, in this tubule. They show quite distinctly 

 a small achromatin mass around each chromatin granule and these 

 are all distinctly connected to each other by Strands of the same 

 material (Figs. 4 and 5 c). Any of these nuclear structures we can 

 find in cells at the margin or in the center of the tubule, although 

 certain of them, a and 6, are more abundant in the former region. 

 In fact these two stages we never find at any distance from the 

 margin except in the distal part of the tubule. In most of these 

 early stages the nucleolus is quite prominent^ and in many (Fig. 6) 

 reaches, relatively, a very large size. We find that nuclei of the 

 same size may have a large or a small nucleolus, but we were 

 unable to distinguish any relation between relative size of nucleus and 

 its nucleolus, to the stage of development. In darkly stained slides 

 the nucleolus would be dark, but when the stain had been well 

 washed out of the section, it either had no color at all or a very 

 slight tinge; in all these sections the chromatin granules were dark. 



With the increase in distinctness of the Strands we find a de- 

 crease in the size of the chromatin granules, they become small and 

 loose their regularity of position within the nucleus. This tubule 



