RECONSTITUTION IN DISARRANGED STENTORS 221 



and the striped surface comes to have the appearance of fields seen 

 from the air. Randomness can be increased by first cutting the 

 cell transversely and rotating the anterior half iSo"" on the posterior; 

 after healing, then recutting longitudinally and rotating the left 

 half on the right. Quarters of the cell are thus transposed and 

 disoriented before the mincing. 



In some of the first experiments of this type (Tartar, 1941a, b) 

 it was found that stentors with two heads or two tails could be 

 produced from singles, and an analogy was drawn between this 

 result and the consequence of inverting embr^^os in the 2-celled 

 stage, by which twins are produced. Weisz (1951a) had found that 

 excessive cutting injuries in grafting only resulted in death of the 

 specimen, but evidently the conditions of experiment were not 

 optimal. Further studies (Tartar, 1956c) revealed remarkable 

 reconstitutions and allow us to say something of how they are 

 brought about. 



After minceration a stentor has a knobby or fascetted appearance 

 from the patchiness of the striping, which again substantiates that 

 the over-all shape of the cell is determined by the arrangement of 

 the ectoplasmic striping (Fig. 63A). Within a few hours the patches 

 begin reorientation, with their striping becoming more or less 

 parallel. Although this point could not be tested, it seems likely 

 that the arrangement of pieces becomes homopolar, like so many 

 tiny magnets. The gradual nature of this process suggests that the 

 position of the new polar axis is established statistically at first, 

 by any group of patches which by chance happens to be similarly 

 oriented and therefore can form a " field " whose influence might 

 then spread to adjoining sections to bring them into corresponding 

 orientation. With this shifting, patches soon appear much larger 

 than originally, and this can be attributed to their joining together 

 as they come into parallel and homopolar orientation. Areas 

 bearing wide pigment stripes do not form a continuous structural 

 union with fine-stripe areas, but only Hke with Hke. Although it 

 would be difficult to observe minor resorption of patches, it is 

 apparent that there is no large scale dedifferentiation. 



As the cut areas move so their stripes become parallel, a visible 

 polarit}' appears as the mass elongates in one direction and a hold- 

 fast appears at the end of a projecting point. Oral regeneration 

 never begins until a definite locus of stripe contrast of considerable 



