BLACKMAX: THE SPERMATOGENESIS OF SCOLOPENDRA. 107 



One of the most important properties of the centrosome is said to be 

 its influence over the separation of the chromosomes and over cytoplas- 

 mic cleavage. In considering the separation of the chromosomes in 

 Scolopendra, it must he admitted that very little power is necessary for 

 its accomplishment ; for, as we have seen, during certain prophase staj 

 the chromatids are already practically distinct bodies with well-marked 

 spaces existing between them. They are at this stage apparently very 

 loosely bound together by linin fibres. Later, when the chromatin 

 becomes of a liquid or viscid consistency, it is generally admitted that 

 these cleavage planes still exist, although they are masked by the greater 

 condensation of the elements. It is therefore probable that the cohe- 

 rence of the various chromatids of the tetrad may be very easily over- 

 come. Indeed it is conceivable that in some cases it may require no 

 external influence to perfect the division. In Scolopendra the separation 

 of the halves of the chromosomes occurs at the time of the lengthening 

 of the cell, and is apparently inaugurated, not by the contraction of the 

 mantle fibres of the spindle, but by the divergent movements of the 

 centrosomes. After the division of the chromosomes and when they 

 have very perceptibly moved apart, the mantle fibres contract and draw 

 them farther toward the poles. Until the separation is well marked 

 the distance between chromosomes and centrosomes is apparently not at 

 all diminished, but later the contraction of the mantle fibres is shown by 

 the approximation of these two classes of elements and by the enlarge- 

 ment of the centrosphere. 



B. Archoplasm. 



Persistence of Archoplasm. — The behavior of the archoplasmic struc- 

 tures in Scolopendra supports in many particulars Boveri's well-known 

 archoplasm hypothesis. During all stages of continued mitotic inactivity 

 in Scolopendra the presence of definite archoplasmic substance is shown 

 by special aggregations of a granular or reticular substance much re- 

 sembling the ordinary cytoplasm but differing from it in several impor- 

 tant particulars. This archoplasm is distinguishable from the unmodified 

 cytoplasm by the closer aggregation of its component granules and by 

 its different reaction to stains. These masses are most conspicuous dur- 

 ing the growth period of the spermatocyte and during the vesicle stage, 

 but they are also quite marked in the early stages of the spermatid. 



At all stages immediately preceding and succeeding mitosis, masses of 

 archoplasm are not to be found, but the presence of archoplasm is shown 

 by the different character of the cytoplasm. It is plainly evident that it 



