142 C. M, CHILD 



eyes, while at the lower temperature none are normal and only 46 

 per cent form eyes at all. In the c-pieces the difference is even 

 greater than in the 6-pieces: here 10 + 62 + 14, 86 per cent in 

 all form eyes at the higher temperature and only 12 per cent are 

 anophthalmic or headless, 2 per cent having died: at the lower 

 temperature 14 + 2, 16 per cent form eyes, 80 per cent are anoph- 

 thalmic or headless and 4 per cent have died. Moreover, at the 

 lower temperature no normal and only 14 per cent teratophthalmic 

 forms appear, as compared with 10 per cent normal and 62 per 

 cent teratophthalmic at the higher temperature. 



In the d-pieces, however, the temperature effect is again much 

 less. At the lower temperature 8 per cent are normal, 64 per cent 

 teratophthalmic and 14 per cent teratomorphic, a total of 86 per 

 cent with eyes, while at the higher temperature 78 per cent are 

 normal and 22 per cent teratophthalmic, a total of 100 per cent 

 with eyes. This effect in the c?-pieces is very similar to that in the 

 a-pieces, although somewhat greater. In the a-pieces the changes 

 all lie between teratophthalmic and normal eyes and in the d- 

 pieces this is true for 72 per cent, only 28 per cent being shifted 

 by the higher temperature from the teratomorphic, anophthalmic 

 and headless columns to the teratophthalmic or normal. In the 

 6-pieces, on the other hand, 54 per cent are shifted by the higher 

 temperature from the anophthalmic and headless groups to the 

 groups with eyes and in the c-pieces 68 per cent are shifted in the 

 same way. 



It is evident from this series, as from the KCN series above that 

 a given external factor produces very different effects at different 

 levels of the body and that a marked difference in the reaction of 

 the posterior region of the first and the anterior region of the sec- 

 ond zooid to the factor concerned exists. In other words, the 

 effect of a higher temperature in increasing the regulatory capa- 

 city of pieces of worms kept at low temperature before operation 

 increases from the anterior to the posterior end of the first zooid 

 and is again much less in the anterior region of the second zooid. 

 The reasons for these differences will appear later : at present these 

 data serve merely as evidence for the existence of a dynamic 

 factor along the axis of the body, which shows not only a grada- 



