162 C. M. CHILD 



microscope is necessary. In most of my experiments by the 

 direct method 100 cc. Erlenmeyer flasks have been used. After 

 the worms or pieces are introduced the water is poured off and 

 they are filled with the solution to be used and corked, leaving 

 only a small bubble of air beneath the cork to prevent bursting 

 with slight changes of temperature. In this way loss of the 

 substance is reduced almbst to zero. Moreover, the flasks pos- 

 sess another great advantage: objects inside the fluid-filled flask 

 except those on the inner surface of the glass on the side toward 

 the observer, are magnified to a considerable extent. With a 

 little practice the flask serves as well as a dissecting microscope 

 and the condition of small animals or pieces can be seen very 

 clearly. 



In using the direct method, where death and disintegration 

 occur within a few hours, we may either record only the time of 

 disintegration, i.e., either of the beginning of disintegration or of 

 complete disintegration, or we may follow the course of disinte- 

 gration and compare different stages. Since death and disin- 

 tegration occur at different times in different regions of the body 

 the second method gives more satisfactory results: instead of 

 recording only the beginning or the final stage, it gives a series of 

 observations on the same material and so not only permits closer 

 comparison of the different lots but increases the value of the 

 results obtained. 



In the course of my work with this method I have gradually 

 come to distinguish five stages. The limits of each stage are of 

 course arbitrary and some of them may, if desired, be further sub- 

 divided. These stages are as follows: 



Stage I. Intact, not showing any appreciable disintegration. 



Stage II. This stage is intended to record the first appearance, 

 of disintegration in any part of the animal or piece. In whole 

 animals the first traces of disintegration usually appear in the 

 head reagion, sometimes in the most posterior zooid. At this 

 stage the disintegration is usually sharply localized and other 

 parts of the body are intact and often show motor activity. 



Stage III. This stage is not very sharply marked off from 

 Stages II and IV. It is intended to include that interval between 



