REGENERATION 123 



feeding organelles to be produced in an enormously wide range of 

 sizes. It seems that nature herself has already explored these 

 possibilities, for the tiny, blue-green Stentor tmdtiformis appears 

 in almost every respect like the tiniest regenerate of coeruleus. 



6. Adjustments to proportionality of parts 



Tiny fragments form primordia which are very short though 

 apparently of normal width and therefore regenerate a set of feeding 

 organelles proportionate to their size except that the individual 

 membranelles are relatively large. In the other extreme, Balbiani 

 (1891b) noticed abnormally large mouthparts in some of his 

 double monsters and I, too, have occasionally seen the same, as 

 well as very large frontal fields and unusually long membranellar 

 bands in the products of stentor grafting. Hence the normal upper 

 limit in size of these organelles can also be exceeded. 



When regeneration is induced by excising the mouthparts only, 

 the new membranellar band joins with the old one. Therefore one 

 might expect that when the entire head is removed the regenerated 

 membranellar band would be smaller ; but in this case the primor- 



FiG. 30. Proportionality of parts in S. coeruleus. 



Anterior half of transected stentor is at first too short and with 

 too-large head. Membranellar band and frontal field are then 

 reduced to half original size without primordium formation, as 

 the cell extends and a new tail-pole and holdfast are formed. 

 Posterior half is at first too long, then regenerates a smaller set of 

 feeding organelles, as the posterior pole is proportionately 

 reduced. (After, Morgan, 1901a.) 



