384 JOHN F. FULTON, JR. 



1). In many other echino(l(!nns Asteroidoa, Ophiuroidea, 

 Echinoidea, and Holothuroidea, there are found pigmented 

 body-fluid cells which likewise give rise (in part at least) to the 

 external pigmentation by becoming deposited in the epidermis. 



Part II. 



In the preliminary observations of the present work, it was 

 found that in nearly every ' invertebrate investigated there 

 occurs in the blood a chromogen — either completely formed, 

 or in the process of formation — which is similar to, and not 

 infrequently identical with, the pigment of the epidermis. 

 Though this in itself is an interesting fact, it is at once apparent 

 that behind the phenomenon there lies something of much 

 greater significance : Why should the body-pigments occur in 

 the blood-system, and whence do they come ? The pigments 

 of the invertebrates, so far as they have been investigated, 

 appear to be derived very largely from food, being absorbed 

 into the blood-stream and carried by that tissue to the epidermal 

 regions, where they are deposited. 



The more specific conclusions are as follows : 



1. In the absence of a blood-system, as in the Echinoderms 

 and lower forms, the nutritive fluids supply the epidermis with 

 its pigments (Part I). 



2. The coloration of several nemertean worms is due to the 

 presence of haemoglobin in the epidermis and in the blood. 



3. In certain nudibranchs (Chromodoris zebra) and 

 cephalopods, pigments are found in the blood-stream which 

 are identical with the epidermal pigments. There is strong 

 evidence that the pigments of the blood-stream of the Mol- 

 lusca owe their origin to the chlorophyllous substances taken 

 in as food. 



4. The lipochromes of annelids are derived from food 

 substances, being absorbed into the blood-stream and trans- 

 ported to the epidermis. Annelid haemoglobin is found both 

 in the blood and in the epidermis. 



5. The enterochlorophyll found in the liver of many crusta- 

 ceans and molluscs is of vegetable origin. There is evidence 



