i:S OF TOXOI'NEO I !.- VARIEGA1 5. 197 



that a -harp differentiation of plasma and chromosome- i- im- 

 possible. 1 ollowing Dr. Stevens's suggestion, I tried to bleach 

 tin ii with H^i >.,, a method -ucce--fully applied in -ome 



other cases, I. ut entireh useless in Arbacia. I therefore gave 

 up further -tudv of the chromosomes of tin- -peci. - 



-OPNEUSTES VARIEi.A I l -. 



'I In- o|,-rr\ at ion- were made on two series of ruu> from \\\ 

 different loealiti' from Beaufort, X. C., the other from the 



Tortugas. The results obtained are the same for both. I U . 



\\iih the -iul\ ol the chromosomes in the first segmentation 

 -pindle ami found in . neustes as Baltzer ('09'," had done 



in nd l:<>::nus a considerable variation in 



the length and form of the chromosomes. 



As iii / and St ntrotns there are t\\o i-\tremel\ 



Ion- chroino -"in. ~ in -.n h daughter plate. Their beha\ ioi -i, 

 -einM< - that dt-iiil.td \>\ I'.alt/er in thai these long rod-bha 

 < linimo-c.iiu-- lair in .splitting and moving to the p< >li s 



ii|>an- Tc\t i ,ith Balt/er's '090. 1M. XXX\ II.. i 



5. </ and I hr-r In i ncs may also be seen in my l-'iu;-. i, 



_ and ; v Sonietinii- the-e long chromosomes are contra. 

 inoiv and then ajipear thicker and shorter (Fig. I, a, the lett pair 

 nt Ion- rod--haped chromosomes). 



A t\; hroiiio-oinc of |>eculiar shajx-, found in all of the 



in- \\hi<li i- n-nally \'-shajK'd, but sometimes more 

 horseshoe-shape* -. 4 and 5). Very frequently in late ana- 



pha-t - tin- t\\o arm- are |.arallel. or nearly so, and one may 

 p.niK o\ ( -rlie the other, I nit there is hardly ever any doubi 

 to \\hether there i- oiu .hroinosome with two arms present or 

 tuo -eparate rod -h.iped ones (Fig. 3, a and b). As may l' 

 O|P- r\ed from I [g. 4 tin- length cf the two arms in these chro- 

 iiio-oine- ma\ \ 'i^htly when the arms are lying in OIK 



optical plane. I tried to determine whether this different! i- 

 confined onl> to certain chromosomes or to chromosome- in cer- 

 taii l>ut no regularity seems to exist. The probable origin 



of the difference in length will be discussed la 



Ihe-. V-shaped chromo- . r in all tertili/ed 1<>.\<>{>- 



ncii nd tin either two or three present. .\mon w ;. ( 



