NATURE OF EXCRETORY PROCESSES IN MARINE POLYZOA. 125 
way to the action of the same pigment; and that the taking 
up of the pigment by particular tissues may have a definite 
relation to the normal pigmentation of those tissues. 
The bearing of this fact on the results arrived at by Hisig,' 
with regard to the excretory value of certain normal pigments, 
will be subsequently pointed out. 
I. Tue NorMaAt CHARACTERS OF THE LivinG ZowciuM IN THE 
SPECIES INVESTIGATED. 
a. Bugula neritina, L. 
This species, which is well figured in its natural colour by 
Costa,? is very common at Naples; the specimens examined 
by me being, as described by most authors, invariably destitute 
of avicularia.2 The colony, as is obvious from Costa’s figures, 
possesses a dark colour which varies from yellowish brown to 
purple.4 The characteristic colour is almost entirely due to 
the presence of a pigmented funicular tissue, already noticed 
by Costa.’ This tissue is shown in PI. III, fig. 17. 
It will be noticed that the funicular tissue agrees with that 
1 H. Hisig, “ Monographie d. Capitelliden d. Golfes v. Neapel,” ‘ Fauna and 
Flora . . . . G. v. Neapel,’ xvi Monogr., 1887 (see especially the ‘‘ Physiolo- 
gischer Theil’’). 
2 QO. G. Costa, ‘“‘ Fauna del Regno di Napoli,” ‘ Zoofiti,” Napoli, 1838, Tav. 
v, fig. 1 [belonging to the chapter headed ‘‘ Ordine III. Cellariee”’]. 
3 A. W. Waters (‘Ann. and Mag. Nat. Hist.,’ ser. 5, vol. xx, 1887) de- 
scribes an Australian form of this species in which numerous avicularia are 
present. 
4 For an account of the pigments of B. neritina see MacMunn, ‘ Quart. 
Journ. Mier. Sci.,’ xxx, 1890, p. 78, and the reference there given to 
Krukenberg. 
5 Costa, loc. cit., p. 15. The zoccia are described as being “ ripiene di 
sostanza granellosa, tinta di rosso di tutte le gradazioni.” 
6 See W. J. Vigelius, ‘Biolog. Centralblatt,’ ili, 1883-4, p. 708; and 
his larger work, “Die Bryozoen ... . ‘ Willem Barents,’” ‘ Bijd. tot de 
Dierkunde,’ 11¢ Aflev., 1884 (‘‘ Parenchymgewebe ”), and other writers. 
