184 BIOLOGICAL LECTURES. 



The body is so transparent as to admit of its structure being 

 studied in minutest detail. The protoplasm of the body shows 

 a fine ramification from the centre outward to the periphery. 



The ultimate branches of the protoplasm spread themselves 

 over the whole inner surface of the animal. The central mass 

 of the protoplasm and its ramifications are constantly moving 

 and changing ; larger branches becoming thinner ; thinner 

 branches becoming thicker by borrowing material from their 



FIG. 4. Noctiluca miliaris. (After Leuckart and Nitsche.) 



neighbors. The protoplasm is highly contractile, so much so 

 that when the organism is stimulated energetically, the minute 

 branches along the periphery contract so violently as to tear 

 themselves completely from the external membrane. 



The most interesting phenomenon in this connection is the 

 close correlation of the phosphorescence with contraction, as I 

 have already said. This Quatrefages proved by two sets of 

 experiments, the one tried in the daytime, and the other at 

 night. Thus, the action of heat, electricity, compression, and 



