SPERM ATOGENESIS OF THE MVKIOPODS. 155 



each clement can be traced from the early prophase of the first 

 spermatocyte to the anaphase of the second maturation division. 

 In other word-, it is evident that during this very important 

 period of their hi-tory the chromosomes show complete individu- 

 ality. In other namely, in the spermatogonia and during 

 the Drouth period, it cannot be claimed that the continuity of 

 the clironio-ome- is actually demonstrated in Scolopoidra, al- 

 though e\idencr -trongly supporting such a vie\v undoubtedly 

 exists. 



SlM MARY. 



The ( hroino-ome ^roup of the primary spermatocytes of Scolo- 

 f>i-inlni ln-r<>\ i- made up of sixteen bivalent chromosomes tetrad- 

 and one uni\ alcut chromosome (dyad), the accessory chnnno- 

 some. 



The i liromo-.oin< - -how such constancy in shape in tin- pm- 

 pha-e and inetapha-e of the primary spermatocytes, and in their 

 relation i., tin- mantle fibers of the first maturation spindle, that 

 tln\ -eein naturally to group themselves under four di-tinct 

 t\l" I In -. ma\ lie designated respectively, as the cn>--- 

 -haped t. -trad-, the double- Y-shaped tetrads, the nxl-shaped 

 tetrad-, and a -in Je-n Kl-shaped dyad. 



Tin- cro liaped tetrads arc six in number and may be ar- 

 ranged in led series as regards size, the difference in bulk 

 beini; -nun ientl\ ^reat to allow the individual chromosomes of 

 thi- t\pe to be di-tiiuui^hed. ( )ne of the chromosomes of thi-> 

 t\pe tin lai:ce-t one can furthermore often be identified by it> 

 I. ml. in \ to la- behind the others during the early metaphase. 



I i\e of the tetrad-* are of the double-V shape. The individual- 

 of thi- t\|.e al-o ma\ be distinguished by differences in bulk. 



The rod--haped tetrads are present to the number of li\e. 

 Tlu'M- sho\\ con-taut -i/.e relations and may readily be arrant l 

 in a graded -erie- as regards magnitude. One of the tetrads <>l 

 tin- t\pe differ- from the others in the form it assumes during 

 actual di\ i-ion. It -eem- to divide transversely, while the others 

 are di\ idin- longitudinally. 



The accessory chromosome is univalent and passes to one of 

 the -econdary -permatocytes without divi-ion. During the 



