382 JOHN F. FULTON, JR. 



upon the pigments of plants. The further relation of chloro- 

 phyll to the bile and urinary pigments is a subject which will 

 well repay further investigation. 



In conclusion it may be said with reasonable 

 certainty that many animals and probably man 

 do normally use the four pyrrol groups of the 

 chlorophyll molecule to synthesize haemoglobin 

 and allied pigments; however, though most 

 evidence points in this direction, no one has 

 actually demonstrated that the animal body 

 is itself incapable of synthesizing haemoglobin 

 in the absence of chlorophyll. 



8. Conclusions. 



Part I. 



What deductions may be made concerning the animals 

 which have thus far been considered ? In the first place it 

 must bo recalled that in no case has the writer dealt with 

 forms which have a true blood-vascular system. 



The most important function of the blood-system in the 

 higher animals is that of carrying nutriment to the tissues. 

 In the lower invertebrates this function is accomplished either 

 by the direct contact of the tissue with the surrounding sea- 

 water, or l)y circulatory fluids — less highl}?- specialized than 

 blood — which move within the body. These fluids, therefore, 

 are the ones which represent the functional antecedents of the 

 blood-vascular system ; and it is to these that one should 

 look in seeking the origin of many of the body-pigments. From 

 the foregoing pages the following conclusions seem reasonable : 



1. The pigmented protozoans owe their colour, probably in 

 every case, to an algal pigment which has resulted from an out- 

 side infection, 



2. Though the evidence in the Porifera is not conclusive,^ 



^ The evidence recently adduced by Van Trigt (1918) removes any 

 reasonable doubt concerning the chlorophyllous nature of the pigments of 

 a large nujnber of sponges. 



