30 



capsule and the collar surrounding the hole In the capsule, 

 through which the tubule Is everted. Let us now follow the 

 interaction of the forces Involved in the behavior of these 

 changing structures. For this purpose we shall divide the 

 explosion into four stages. 



Stage 1. The eversion of the outer cavity of the tuhule 

 (Pig. 67). Two forces probably take part in this, the pres- 

 sure in the capsular cavity and the elongation of the central 

 body. 



Stage 2. The elongation of the everted outer cavity (Pigs. 

 68 to 71 and 76). This results in the formation of the collar 

 (Pig. 68,r.). Here again two forces may be involved, the 

 swelling of the material in the capsular cavity and the fur- 

 ther elongation of the central body which stretches the por- 

 tion of the inner tubule which bounds the inner tubular cav- 

 ity. The fact that the everted portion is sometimes longer 

 in the axis through which the central body passes indicates 

 that this body may be exerting an out-pushing force. If this 

 is the case, we have here an elastic body that has become 

 active by being released from compression, that is the central 

 body elongates like a coiled spring. This action is fully 

 discussed by Koltzoff . The pressure in the capsular cavity 

 is sometimes showa by the squeezing of the central body out 

 through the outer end of the tubule when it has lost its re- 

 sistant properties. 



Stage 3 . The second eversion of the inner tubule (Pigs. 

 77 to 79). Prom the condition shown in Pigs. 71 and 76, the 

 increasing pressure in the capsular cavity causes the wall 



