712 William Patten 



and Protozoa. Moreover we know that light is of the utmost importance 

 for the contiuuation of plant life. These consideratious , together with 

 innumerable others, render it almost certain that the efifeet of sunlight 

 lipon the animai organism is a beneficiai one. We h a ve , th er e f o r e , a r- 

 rived at the eonclusion thatpigment isthe receptacle of the 

 beneficiai effects of the sunlight upon animai organisms. 



The most modified form of pigment is probably black: between 

 this color and the brown, yellow, and green, there is a complete grada- 

 tion. We find the yellow and green colors most abundant in the lower 

 auimals, while the black and brown are less common. 



In the development of the higher animals. as in Mollusca, the 

 pigment first appears as colorless graniiles, or plastids, 

 which become yellow, yellowish green, brown, and finally 

 black. 



In the Protozoa and even in some worms , a green pigment re- 

 sembling Chlorophyll, and probably having a similar function, is found. 

 These facts: (1) the tendency of pigment granules to form niany inter- 

 mediate stages between undoubted animai pigment and plant pigment, 

 and consequently the difficiilty in many casesofdistinguishing between 

 the two; (2) the greater resemblance, initsearly stages of development, 

 of highly developed animai pigment to Chlorophyll; and (3) the almost 

 complete identity in function between animai, and plant pigment, lead 

 US to conclude that animai pigment and Chlorophyll , are ex- 

 treme modifications of the same structures. We can therefore 

 say that Chlorophyll absorbs from the sunlight the energy necessary 

 for the trausformation of inorganic into organic matter : without this sup- 

 position vegetable matter would be a living contradiction to the theory 

 of conservation of energy, for we would bave to suppose that vegetable 

 protoplasm itself coiild create the force necessary for the conversion of 

 inorganic salts into organic matter. But the same reasoning will apply 

 equally well to animai protoplasm: it, also, must absorb, in some 

 way, the force necessary for the conversion of matter into higher Com- 

 pounds, and one way of doing this is by the absorption, not merely of 

 beat, but of chemical rays, or more simply, of energy from the sunlight. 

 In plants, this sun energy is used in the Chlorophyll grains, for in them 

 the production of organic matter takes place. But in animals it is 

 probable that the pigment granules are only the receivers of the energy, 

 the beli ophags as we shall cali them. while this energy is transmitted 

 by nerve fibres to centres where it is consumed in the production of 

 protoplasmic compoimdsw When a sufficient amount ofenergyhasbeen 



