BEHAVIOR OF NUCLEUS AND CHROMOSOMES. 157 



processes apparently go together. As the chromosome thickens, 

 the surrounding layer thickens, increasing the diameter of the 

 lobe in that region. This process gradually progresses up to the 

 prophase, when, as the chromosomes approach their maximum 

 condensation the lobes become decreased in size. In the late 

 growth period there is a suggestion of a secondary lengthening 

 out of the chromosomes and the lobes into a more ramifying con- 

 1 it ion such as exists at an earlier stage, but the change is not 

 extreme, and may not be constant. It suggests, ho\vever, the 

 stage in Asilus sericens (I. c.) in which the threads spread apart 

 after undergoing contraction. This also occurs relatively late 

 in the growth period. 



In Lasiopozon there is no "contraction stage," such as occurs 

 in Asilus; but throughout most of the growth period there are 

 some indications of a polarization of the threads toward the 

 nucleolus; and often faint connections are to be seen between tin- 

 two (Figs. 7 and 8). 



I Hiring the prophase, and up to a late stage in metaphase, the 

 hyaline layer around the chromosomes remains conspicuous, as 

 shown in Figs. 10 i.v The spindle fiber may often be traced t 

 projection of this layer corresponding to that of the chromosome, 

 and thence through the layer to the chromosome. 



Not enough nnaphase figures are present in our material to 

 permit us to follow the chromosomes through this st. 



During the late growth period and the first sperm. iu>. \ u- divi- 

 MIUI the mitochondria become very prominent, and by darkening 

 tin- r> toplasm, aid in bringing the outline of the chromosomal 

 sheath into relief. In metaphase large mitochondri.il n><l- are. 

 1 1 < < iiiently present which are almost as dense as the chn>m< >s< m 

 These are seen longitudinally in Figs. loand i; v .iml in trail-verse 

 section in Figs. II and 12. It is to be noted that they are not 

 surrounded by a hyaline cortex comparable to that around the 



chromosomes. 



THE XUCLEOLUS. 



The nucleolar behavior during the growth period is somewhat 

 different in our two specimens. In one (2056) there i> a single 

 nucleolus in the early growth stages.while in the other (2055 1 

 there are two. In the following description the two specimens 

 are considered separately. 



