202 



The Structure of Protoplasm 



adheres to the sHde. The small space between the two partitions is 

 filled with a 2 per cent agar sol at about 40°C., the meniscus of which 

 is higher than the upper edges of the partitions. Before the agar is 

 transformed to a gel, which occurs at about 35°C., the glass slide 

 with the agar sheet and the dumbbell-shaped plasmodium is inverted 

 over the chamber. As the agar is still in a sol state, it fills up all the 

 spaces to be closed without injuring the delicate strand of protoplasm. 



After this procedure the 2 per cent 

 agar soon gelatinizes, and the 

 chamber is divided into two air- 

 tight compartments. Figure 3A 

 shows a cross-section through the 

 double chamber at the agar wall 

 and Figure 3B, its longitudinal 

 section at the iniddle part. 



Protoplasmic flow^ is stopped 

 temporarily because of mechani- 

 cal and thermal disturbances, but 

 it soon recovers. Meanwhile, the 

 two blobs of protoplasm at both 

 ends of the strand, which are in 

 the separate compartments, spread 

 out, having already fused with the 

 connecting strand (Fig. 4A) . 

 The observation chamber is now 

 put, with rubber gaskets, between two metal frames which are 

 tightly joined together by means of four screws. Thus is the pre- 

 paration of the material accomplished (Fig. 4B) . 



It is a favorable characteristic of agar to have a large hysteresis 

 range, within which agar can exist either as a sol or as a gel. Two 

 hardly compatible technical requirements are thus fulfilled; namely, 

 the two separate compartments are kept air-tight against a consid- 

 erable pressure difference between them, and at the same time the 

 cross-wall does not block the flow of protoplasm in the delicate 

 connecting strand. Furthermore, agar is sufficiently transparent to 

 permit observation of the flowing protoplasm in the connecting 

 strand. It is by means of light transmitted through the agar wall that 

 the observation is made. Though it is not absolutely necessary for 

 simple observation of flow, one can get a clearer microscopic image 

 of the connecting strand if a rectangular prism of glass of suitable 

 size is mounted in the agar wall between the two partitions. 



Fig. 1. A. An agar sheet, ag. with 

 a protoplasmic strand, st, placed on a 

 glass slide. B. Two protoplasmic 

 masses placed on the agar sheet at 

 both ends of the strand. 



