i9o8] YAMANOUCHI—SPOROGEXESIS /.V NEPHRODIUM 9 



the sequence of mitosis preceding the formation of the nucleus of the 

 spore mother cell is exactly the same. 



Sporo genes is 



Ik 



Presynaptic stage. — The chromatin reticulum in the resting 

 nucleus of the spore mother cell has the same structure as was just 

 described for the nucleus of the sporogenous cell; the size of the nu- 

 cleus, after its full growth, is greater than that of any nuclei of the 

 Sporogenous cells, and not infrequently it occupies almost all of the 

 cell. No regularity could be found in the massing of the chromatin 

 material; at certain points there are dense masses and at others almost 

 none at all. Nucleoli, one to several in number, are always present in 

 various locations, without any physical connection with the chromatin. 



The exact structure of the chromatin reticulum needs description. 

 It is an anastomosing complex of ragged clumps and irregularly 

 branched strands (fig. ij) ; the former always stain deeply and the 

 latter lightly, simply because of the difference in compactness of 

 massing. They originated from a single source — the chromosomes 

 of the previous mitosis — by the vacuolization process described 

 above. 



The clumps of the reticulum lose gradually their ragged look, 

 because of the disappearance of the fine strands, the elongation of the 

 clumps in certain directions, and the migration of material from the 

 clumps to some of the fine strands so as to thicken them (fig. 150). 

 All these changes tend to transform the ragged structure, but they do 

 not occur simultaneously throughout the reticulum, so the whole is 

 still plainly a reticulate structure, as seen in fig, 16. Nevertheless, 

 in regions where the reticulum is being converted into thread structure 

 there are visible parts of threads running closely side by side (fig. i6a). 



■The transformation of the reticulum into a thread 

 structure now proceeds rapidly. When the transformation is nearly 

 completed (fig. 17), parts of the thread are not smooth and uniform 

 in appearance and thickness, and in its course it is greatly tangled. 

 These tangled masses of thread begin to contract and become localized 

 nn c\nf^ ^\Af^ f^f tVi*^. niTr-lp^ar rnviK- n T)Tnce<^<^ w^hirh marks the mitiation 



the sMiaptic state. Preparations stained with iron-alum 



-Uu 



ylin and extracted to a certain degree of differentiation oi the stams 



