360 JOHN F. FULTON, JR. 



PART 11. THE PIGMENTS OE ANIMALS WHICH 

 HAVE A BLOOD-VASCULAPt SYSTEM. 



1. Introduction. 



Ill tlio lirst half of this study covisich^ration was given to 

 (hoso invertebrates which possess no blood-vascular system, 

 and the general conclusion was reached tliat the body-pigments, 

 in the absence of such a system, are deposited in the organism 

 by its nutritive* fluids. It was concluded also that the materials 

 used in the production of pigment are derived from certain sub- 

 stances — usually chlorophylloid — which are taken in as food. It 

 seemed, therefore, that in the lower invertebrates the body- 

 fluids (which serve the nutritional function of the blood of 

 higher animals) serve also to supply the organism with the 

 substances from which it elaborates its pigment. In echino- 

 derms, for example, the pigment is formed in the perivisceral 

 fluid, and is subsequently carried to the epidermal regions. 

 As a result of such observations one might reasonably expect 

 the blood of the higher animals also to furnish the supply of 

 materials for the body-pigments. The writer, in consequence, 

 has examined the evidence to determine whether such a deduc- 

 tion is justifiable ; the results of the investigation are presented 

 in the present half of the paper. 



2. Nembrtina. 



Though the nemertean worms possess certain annelid 

 aflinities (nephridia, (fee), the balance of morphological evidence 

 places them close to the Turbellaria. In one very important 

 characteristic, however, they are distinct from all of the 

 Platyhelminths, and that is in the possession of a well- 

 developed blood-vascular system which is entirely closed. 

 The vessels originate from a fusion of the spaces which arise 

 in the mesoblast. The circulatorv fluid contains flat, nucleated 

 corpuscles, and it is propelled through the body, probably by 

 bodily contractions, though there is some evidence of vascular 

 peristalsis. Eew investigations have been made upon the 



