OF THE MYRIOPOP>. 147 



the shorl arm f.f the cross is drawn out and to apparent differences 

 incident to tin- an;Je of vision. When the short arm of the cr 

 i- drawn out hut little the tetrad approaches the rod-shaped 

 ( hromosomes of type C. Then, too, the cruciform tetrads vary 

 in -li.ipc in <!iti. rent stages of the metaphase. The limbs of the 

 re more likely to be of nearly equal size in the early spindle 

 ill. m uhen division has actually begun. As the chronio- 

 son n in i lie same equatorial plate, are not all in exact ly 



tin- same staj division at the same time- this factor should 



M i\ e ' 'ii-ideration. 



An at ii-mpt u a- made to learn whether any of the chromox imes 

 i on-taiitK either lag behind or precede the others in division. 1 1 

 \\a- found that chromosome A, the largest of the cross-shaped 

 tetrad-. -ho\\- .i tendency to lag somewhat behind the others of 

 tlii- t\pe. In many of the chromosome groups this is very evi- 

 dent. In -oii;- cells it is not yet oriented in the characteristic 

 manner in the equatorial plate at a time when some of the others 

 ha\e he^un to -hou tlu- characteristic change in shape incident to 

 the eliding apart of their component elements. This can be seen 

 h\ i oiiipaniii; ( hromosome A with other chromosomes of similar 

 t \ pe in 1 [ i. >, 4. etc. Then, too, this chromosome often 

 pre-eiit- a l< lear-cut outline than do the others, approaching 

 tin granular condition characteristic of the prophase. 



1 M tin- i hiomosonies of tyjx' H there are five present in the 

 metapha-c oi >', m'upcndra hcros. This is the type of chromosome 

 uhicli -h..\\- the characteristic double-Y shajx in the propha-e. 

 I he dil!eu-i,.i- in -hape between the tetrads of this type and tin 

 h.iped elements is usually cjuite striking. E\ r en more char- 

 acteri^tic of thi- t \ pe is the attachment of the mantle fibers and 

 the orientation ..f the chromosomes in the equatorial plate. As 

 -i .n in >ide \ ie\\ . the chromosome is more or less rectangular in 

 -hape. hut one end is usually wider than the other and to the 

 angles of tin- .-ml the mantle fibers are attached. The chromo- 

 -oine n-uall> lie- with this end toward the center of the spindle, 

 \\ hile the free end that to which the mantle fibers do not attach > 

 extends oiituard. This free end is often notched and this notch 

 indicate- the plane of longitudinal division. In end view (Figs, 

 i , /. <>. ./. etc. i the appearance is not so characteristic in the draw- 



