136 C. M. CHILD 



indicated in figure 46 by the shaded area, the length of the area and 

 the density of shading representing as before approximately the 

 limits of variation of position and the frequency. In many cases 

 among these worms the second zooid has undoubtedly divided 

 into two, as the results of experiments indicate. 



In all cases the worms had been fed three times a week with 

 beef-liver for at least two months before the experiments began. 

 When the worms are fed as often as this only a comparatively 

 small part of the stock reacts at any one feeding, the others not 

 being sufficiently hungry. I have found by experience that there 

 is no object to be gained by feeding stocks oftener than this when 

 they are kept at a temperature of about 20°C. Hence I have 

 called this maximal feeding. 



All worms used in the experiments, except where temperature 

 was the experimental factor, were kept in the same room at a 

 temperature ranging between 18° and 22°C. and in darkness. In 

 all experiments the controls and the experimental lots were kept 

 under conditions as nearly alike as possible, except for the one 

 experimental factor. 



1. Cyanide and temperature experiments 



Series 432 I and II. November 28 to December 21, 1911. In 

 this series the four pieces a-d, as indicated on the left side of figure 

 46 were used. It will be seen from figure 46 that the pieces a, b 

 and c include practically the whole length of the first zooid except 

 the head, while the piece d consists in large part of the anterior 

 region of the second zooid. In consequence of the variation of 

 the level of fission the posterior end of piece c sometimes includes a 

 small part of the second zooid, while at the other extreme d is 

 mostly within the first zooid. In lots of fifty pieces, however, 

 most of the c-pieces are within the first zooid and most of the d- 

 pieces are largely within the second zooid. If there is a difference 

 in the dynamic conditions between the posterior region of the 

 first and the anterior region of the second zooid it should appear 

 between pieces c and d. 



Lots of fifty each of a, b, c, d were placed in water at a tempera- 

 ture of 18° to 22°C. as a control and similar lots of fifty each were 



