416 C. M. CHILD 



III. In both whole animals and pieces disintegrations of lateral 

 margins of body until it is completed and swelling of body begins. 

 Movement may still occur to some extent in the intact parts. 



IV. Swelling of the body to complete loss of epithelium and 

 loss of shape. Motor activity has ceased. 



V. All further changes after swelling and loss of shape are 

 completed. 



The recognition of these different stages makes it possible to 

 distinguish more clearly slight differences in susceptibility which 

 would otherwise not be evident. 



The numbers in each of the five columns for each time and each 

 lot are the actual numbers of animals or pieces of that lot which 

 are in that stage at that time. Lots of ten each were used and 

 condition was recorded every half-hour in all cases. 



From these tables it is possible to determine at a glance the 

 regional differences in susceptibility and by comparison of the 

 tables for pieces of different size the effect of size and region upon 

 the changes in susceptibility following section appears and com- 

 parison of the susceptibilities of pieces of the same size at different 

 times shows the course of the susceptibility changes. 



II. STIMULATION 



1 . The susceptibility of whole animals 



In order to show how the susceptibility of the pieces changes 

 following section it is necessary to determine the susceptibiUty 

 of whole animals as a basis for comparison. Table 1 gives the 

 susceptibility of a lot of ten worms 18 mm. in length, that is, of 

 the same size and physiological condition as the animals used for 

 the preparation of pieces. 



2. The one-fourth pieces 



The regions of the body represented are indicated in figure 1. 

 Pieces 1 and 2 represent the body of the first zooid and only the 

 records of these pieces are included in the tables. 



