TISSUES OF LIGHT-PRODUCTION 12$ 



of other colors, that is to be seen in some forms of animals, has not 

 been studied as yet, and we are unable to say if these lights are as 

 efficiently produced as is that of the firefly. As has already been said, it 

 can easily be possible that some animals produce a light that we cannot 

 see at all, its waves lying outside of those rays that we can see, in the 

 non-actinic part of the spectrum. 



The production of light by a living being as well as the production of 

 electricity seems to those not accustomed to the idea as a " wonderful " 

 process. Neither one is any more wonderful than the production of 

 motion or of heat. In all of these cases we can easily conceive of these 

 functions if we remember that protoplasm itself does not perform them, 

 but is restricted to the role of making or secreting certain substances that, 

 when they are brought into contact with oxygen or with each other, 

 automatically perform the act. The great thing to understand is how 

 the protoplasm is able to continually secrete these as well as other sub- 

 stances under other than some " vital " law. 



Many animals give off light which is not their own, but which is 

 produced by some bacteria which infest their bodies or which are present 

 in the food in their digestive tracts. This can be seen in many worms 

 and insects, especially some midges which are all aglow during flight. 

 This condition is peculiarly true of many dead Crustacea where a sud- 

 den exposure to oxygen by the turning over of driftwood and jetsam 

 will cause them to all light up. 



Examples of Photogenetic Tissues 



The power of producing light is found in one-celled animals, and 

 the protozoon, Noctiluca miliaris, is probably the best known example 

 of a luminous, one-celled animal. 



This tiny creature appears on the surface of the sea in countless 

 numbers in some localities. Seen in the daytime under the microscope, 

 it shows a reticular cytoplasm through which a great number of granules 

 are scattered. These granules are probably the secretion used to produce 

 light. We shall call them the photochondria. Around the nucleus is 

 an area of cytoplasm which is undifferentiated in that it does not pro- 

 duce any photochondria. Its surface gives off very many fibrils, which 

 extend radially to all parts of the periphery where they are attached. 

 They extend through the photoplasm, and as the animal always contracts 

 and shines at the same time it will not be far amiss to conclude that the 

 photochondria act also as myochondria to the contractile fibrils, or that 

 both kinds of granules are produced by the cytoplasm or photoplasm. 



When examined at night with a low magnifying power, the animal 

 gives off a beautiful light that appears as an homogeneous illumi- 



