NATURE OF EXCRETORY PROCESSES IN MARINE POLYZOA. 161 
organ, as in the case of the green gland of the crayfish, where 
the end-sac excretes carminate of ammonia and the tubules 
excrete indigo-carmine, or as in the well-known case of the 
Vertebrate kidney. Similarly, the facts recorded above with 
regard to the Polyzoa show that the function of taking up 
these and other pigments is by no means restricted to one set 
of cells, —the leucocytes, for instance, taking up indigo-carmine, 
but being quite unaffected by carminate of ammonia. 
Kowalevsky’s results on Nereis are of special interest in 
connexion with my own results on the Polyzoa. In that 
animal Kowalevsky showed! that indigo-carmine is taken up 
principally by the blood-corpuscles, but also by certain seg- 
mentally arranged organs consisting of glandular cells lying 
on the dorsal side, and containing, in the normal animal, 
accumulations of brown or yellow bodies. This latter statement 
agrees closely with Eisig’s results on the excretion of carmine in 
Capitella,’ in which carmine taken up and digested by the 
alimentary canal is ultimately excreted into pigmented granules 
which normally occur in the skin. Eisig shows that there is con- 
siderable reason for regarding the cutaneous pigment of Capi- 
tella and of many other animals as an excretory product.® 
The taking up of indigo-carmine by the cells which have 
been above described as ‘leucocytes ” is analogous to its ab- 
sorption by the blood-corpuscles of Nereis. This pigment as 
well as the others employed may, however, be taken up by 
certain normally pigmented cells occurring principally in the 
walls of the alimentary canal. 
This fact recalls the observation of Chrzonszezewsky‘* that 
Moe: éit p. 71. 
2 “Fauna u. Flora G. v. Neapel,’ Monographie xvi (‘ Capitelliden ”), 1887. 
* The interesting results of H. E. Durham (“The Emigration of Amceboid 
Corpuscles in the Starfish,” ‘Proc. Roy. Soc.,’ vol. xliii, 1888) have not 
much bearing ou my own observations, inasmuch as Mr. Durham investigated 
the ingestion of granules of precipitated pigments by leucocytes, whereas my 
observations concerned the excretion of solutions of pigments permeating the 
tissues. 
4 N. Chrzonszezewsky, “Zur Anat. u. Physiol. d. Leber,” ‘ Virchow’s 
Archiv,’ xxxv, 1866, p. 157. 
VOL. XXXIII, PART I.——-NEW SER, L 
