NATURE OF EXCRETORY PROCESSES IN MARINE POLYZOA. 163 
formation may not be altogether unconnected with the process 
of digestion. Instances of excretory processes carried on by 
the walls of the alimentary canal are, however, by no means 
unknown in other animals. 
In this connexion, too, Hisig’s results on the Capitellide? 
must be further cited. Hisig gives a most elaborate discussion 
of the excretory value of many natural pigments, not only in 
the Capitellide, but also in various other animals.? The facts 
observed by myself with regard to the appearance of indigo- 
carmine and other pigments in cells which are normally pig- 
mented is in complete accord with Hisig’s results; tending to 
establish the conclusion that these normal pigments are to be 
interpreted as, to a considerable extent, excretory in nature. 
As instances of this may be mentioned the deposition of these 
pigments in the granules of the wall of the alimentary canal, 
and in the granules of the funicular tissue of B. neritina; the 
appearance of carminate of ammonia in cells of the type shown 
in Pl. III, fig. 22, these cells also containing natural brown 
pigments ; and the association of indigo-carmine with natural 
pigments in the leucocytes of F. papyrea (figs. 23 and 24). 
The general conclusion of the experiments described above 
is that excretion is performed, in the marine Ectoprocta, partly 
by the cells which have been described as “ leucocytes,” partly 
by the walls of the alimentary canal, and partly by the 
funicular tissue. The so-called “lateral cords” probably play 
some part in excretion, although I am by no means confident 
that this is their principal function. 
A few remarks may be made with reference to Cuénot’s 
recent paper’—the general conclusions of which had been 
1 Loc. cit. 
? T have had the opportunity of looking through the manuscript of a paper 
which is to be shortly published by Mr. H. E. Durham, who has brought 
together a large series of observations tending to establish the same con- 
clusion. (4% jpn p rerding Me A. P/~-/2/, ) 
3 L. Cuénot, “ Etudes sur le sang et les glandes lymphatiques dans la série 
animale. 2e Partie: Invertébrés,” ‘Arch. Zool. Exp. et Gén.,’ 2e sér., t. ix, 
1891, pp. 12 and 365. 
