5PERMATOGENESIS OF THE MVRIOPODS. 143 



coim id.-- with the point of synaptic union of the elements and 

 thai cadi bivalent chromosome during its division undergoes a 

 "change of it- long axis from a longitudinal to a trail-verse direc- 

 tion." Thi- i- accomplished by a rotation of the chromatids 

 over ea< h other in such a manner as to result in a longitudinal 

 division of tin tetrad in the first spermatocyte. In Scolopendra, 



I have -ho\\n in previous papers (op. cit.}, no such complicated 

 process occurs in division. The long axis of the tetrad in mo-t 

 < ases remain- p.ir.illel to the line of longitudinal clea\age and in 

 tin- mci.ipli.i-. the two halves glide over each other during the 

 .HI n| di\i-inii. A- may be seen in the semi-diagrammatic 

 dra\\ii. I I , A) and in several of the chromosomes of this 

 t\pe in tin- .1- < ompanying plates, the two halves of tin- tetrad 

 11 to .idhere raihcr closely and there is often considerable di-- 

 toriion. In I -ig. I. /;, drawn from my preparations direct it \\ill 

 be -ecu ih. n the parts of the two daughter chromosomes remain- 

 in^ longest in I'Hit.ict are considerably lengthened and di-iorted 

 appareinK due to the firm adhesion of the two parts. 



I lie -e< ..ml i\pe of spcTmatocy to chromosome is the "double- 

 V" iiii.id de-cribed b\ me in a previous paper (op. cit.}. This 

 t\pe u-ii. ill\ aii-es from the bivalent chromosomes of the early 

 I 'i i .] ihase \v Inch are bent at a sharp angle at the point of synap-i~. 

 \liei tin lmiv;iiiidinal cleavage of the chromatin thread has oc- 

 < -lined i he doubli- thread becomes shorter and thicker, resulting 

 in the double \ -haped structure shown in Fig. II, r. There i-.n 

 .ill time- .1 very apparent interruption of the chromatin at the 

 .mje n| e. irli Hue, id (point of synapsis), and it is at this point 

 th. H i In cross di\i-ion occurs later. In the late prophase there 

 i- .i -till further condensation of the chromatin and shortening of 

 the Hue. id, re-ulting in the closer apposition of the ends of the 

 t lire. id- l.uthe-t limn the point of synapsis, resulting in a chronx >- 

 -nine of i he -h.ipe -hown in Fig. II, e,f. At the time of the forma- 

 tion ol the -pindle the mantle fibers come to be attached t the 

 di-i.il end- .ml- farthest from point of synapsis) of the tetrad in 

 -nth a manner iFig. II, e, f, ij) that the chromosome i-di\idid 

 along it- longitudinal axis. In this type al^o, the two halves of 

 the chroiiio-oiiie -ec'in to adhere closely and to divide reluctantly 

 Fij II. . //, al-o 1'igs. 6, /, and 17, j). 



