140 C. M. CHILD 



in any given case depends on which of the two factors over- 

 balances the other. In the a-pieces, for example, the differential 

 effect does not play any important part in the total result ; in the 

 6-pieces the two factors are nearly balanced and in the c-pieces 

 the differential effect overbalances the direct effect, except in the 

 normal column and the result is an apparent morphogenetic 

 stimulation by means of a depressing agent. It will be shown in 

 later papers that the differences in the effect of the KCN at differ- 

 ent levels of the body depend first upon the axial gradient and 

 second upon the dynamic changes in the pieces following isolation. 



Turning now to the c?-pieces, we find in lid 10 per cent normal 

 and 82 per cent teratophthalmic, a total of 92 per cent with eyes 

 as against a total of 94 per cent with eyes in Id; but lid shows 

 only 10 per cent normal as compared with 34 per cent normal in 

 Id, and 82 per cent teratophthalmic, as compared with 58 per cent 

 in Id. The KCN has changed 24 per cent of the pieces from nor- 

 mal to teratophthalmic. Here then the effect of the KCN is 

 very similar to that in the a-pieces. The (i-pieces form the ante- 

 rior region of the second zooid and it is clear that they show a 

 marked difference in their reaction to the KCN from the c-pieces 

 which form the posterior region of the first zooid. In this series 

 the remaining parts of the posterior zooids were not included. 



Series 419A 1 and 2? November 2, 1911 to February 1, 1912. 

 In this series the effects of different temperatures on regulation are 

 compared. The worms were collected November 2, 1911, from 

 spring water at 10° to 12°C. and after collection were kept in a 

 refrigerator at 10° to 12°C. until December 23, when the pieces 

 were cut. During this time the worms received maximal feed- 

 ing, although in consequence of the low temperature their reaction 

 to food was slight. 



On December 23 lots of fifty pieces each of a-d, as indicated on 

 the left side of figure 46, were cut in water at 10° to 12°C., but as 



2 This series as given here forms a part of a larger series on acclimatization to 

 different temperatures and its physiological after-effects. The series as a whole 

 shows very clearly that worms which are acclimated to different temperatures 

 possess very different regulatory capacities at any given temperature. The 

 results of this and other similar series give us some insight into the nature of the 

 process of acclimatization. 



