Some Points in the Spermatogrenesis of Mammalia. 141 



we have seen, tlie term attraction sphere does not merely pre-suppose 

 an archoplasm. nor does the term archoplasm necessarily imply the 

 existence of a centrosome; but the manifestations of attractions and 

 lepulsions during mitosis are always supposed to be related to a 

 centrosome or centrosomes, and it follows that to call an archoplasm 

 without a centrosome an attraction spheie would be well nigh an 

 absurdity. 



During rest then, and at the termination of the lung prophasis, 

 the centrosomes and the archoplasm in the spermatocytes of the rat 

 are quite separate from one another. The centrosomes divaricate and 

 assume their usual position at the j^oles of the grouinr/ spindle 

 (Figs. 3. 4. 5), while the archoplasm remains an inactive structure 

 in the body of the cell. AVliat becomes of it? In the papers to which 

 I have already alluded. Van Benedeu and Boyeri figure the structure 

 as dividing, a fairly large portion presumably with a contained centre- 

 some passing into each new cell. Nothing of the kind occurs in 

 the rat; the great irregular archoplasm remains in some position 

 quite outside the seat of dynamical change (Fig. 3, 4rt) accompanying 

 division; and. as the metamorphosis proceeds, it becomes less and 

 less conspicuous, imtil. at about the time when the chromosomes 

 are collected at the equatorial plane, it is nowhere to be found 

 (Fig. 6) — in other words, the archoplasm is re-ahsorhed into the 

 cytoplasm: and foi- a short time after this the cells contain no archo- 

 plasmic hody. the centrosomes lying at the ends of a spindle figure, 

 u-hose fibres have been formed afresh from the surrounding cyto- and 

 possibly nucleo -pilasm. When the division is completed these new 

 fibres again collect as archoplasmic masses (Fig. 10) in the daughter- 

 cells (i. e., the spermatids). It follows, therefore, that in the rat the 

 archoplasm has only a potential relationship with the centrosomes, and 

 that it is connected with them only when it exists as the spindle 

 fibres, or when, strictly speaking, it is not an archoplasm at all. 



Its re-absoiption into the cytoplasm diuing the formation of a 

 fi-esh crop of spindle fibres suggests that it cannot be very distinct 

 fi'om that substance; and this fact incidentally strengthens the opinion 

 now gaining ground that the spindle is often of cytoplasmic origin. 



