GROWTH AND DIVISION 63 



The lateral striping undoubtedly increases in length, though 

 we do not know when or how this occurs. Johnson said that during 

 division the striping at the posterior end of the future anterior 

 daughter cell lengthens as a new tail pole is formed for it. But we 

 do not know, for instance, how new body cilia in a growing longi- 

 tudinal row could be interpolated between those already present, 

 or whether cilia are added only at the end of a row, or increased in 

 number only during fission. 



Increase in the number of lateral stripes is much more obvious. 

 Brauer (1885) first suggested that the shorter stripes which do not 

 run from pole to pole are new ones resulting from multiplication, 

 and that pigment stripes multiply by the interpolation of a new 

 clear stripe was proposed by Johnson (1893). The number of 

 granular and clear stripes increases with the size of the animal. 

 Largest specimens of coeruleiis have about 100 stripes of either kind. 

 Tiny individuals from starving samples which were about one- 

 sixteenth the maximum cell volume had approximately 66 stripes of 

 either type. When a cell divides transversely, the division products 

 have about 80 stripes of each kind at their circumference because 

 about 20 are carried into the frontal field of the opisthe or posterior 

 daughter cell. Presumably, interfissional increase is from 80 to 100 

 as the volume is doubled. The number of stripes thus increases 

 with the volume but less rapidly, some of the surface increase 

 probably being accommodated by widening of the granular stripes. 

 These remarks agree well with earHer conclusions of Popoff (1909). 



A. A case of differential increase in length and breadth of a 

 grafted patch, a: Patch bearing primordium grafted into back 

 of a host from which mouthparts were then excised, b: Primor- 

 dium resorbed but length and number of stripes of the graft also 



promptly increased. 

 B. Shift in relative location of a tube formation, a: Grafted 

 pair developed an adventitious, gullet-like tube, a: In process 

 of reorganization-regeneration next day, with tube now displaced 

 far posteriorly, possibly indicative^ of differential growth and 

 resorption in the ectoplasm. 



C. Problems of growth indicated by another marker, a: 



Grafted pair developed a tube which was resorbed {b) leaving 



patch of dense pigment granules at the surface, c: Specimen 



reorganizing two days later with pigment clot now far to left of 



primordium site. 



