GROWTH AND DIVISION 65 



Stripes were produced (Fig. i2b). From such experiments we may 

 eventually learn how the number of lateral stripes and fibrous 

 bands is controlled. 



Stripe multiplication apparently can occur in any meridian of 

 the cell. When it occurs on the dorsal side where the pigment 

 stripes are wide, the pigmented stripes seem very quickly to attain 

 the width normal for that area after they have been split in two by 

 the interpolation of new clear stripes. Figure 13 thus shows 



Fig. 13. Specimen suggesting that splitting of granular stripes 



in wide-stripe area quickly leads to broadening of these stripes 



in harmony with those adjacent. 



branches of the pigment stripes as wide as the " stem ". This illus- 

 tration also demonstrates that the splitting of the granular stripes 

 can occur in either direction. But the greatest stripe increase occurs 

 at a specific region in the side of the cell where the mouthparts are 

 located. This area has become a key to stentor morphogenesis. 



Brauer (1885) had early described in coeruleus that posterior to 

 the mouth there is a ''fiber which may give up to 10 secondary 

 members lying against each other". Essentially this triangular area 

 is a place where about 25 clear stripes and an equal number of 

 alternating pigmented bands do not run all the way to the posterior 

 pole but are bounded on each side by stripes which do (see Fig. i). 

 Since the stripes become shorter as they approach the left boundary 

 stripe and because that stripe takes something of a diagonal course, 



