REPORT ON SPIRULA. 
25 
V. Excretory System. 
The viscero-pericardial cavity occupies the posterior part of the body, on both sides 
of the central portion of the shell, which divides it almost completely into two halves, 
communicating with each other in front of the last whorl, this communication reaching 
a little backward in Spirilla peronii between the penultimate and last whorl (PL III., 
w", and PI. IY. figs. 2, 4). This cavity encloses the heart and the ovary (the two 
specimens examined being females). The posterior portions of the stomach, although 
projecting into the viscero-pericardial cavity, are situated outside of the “ peritoneal ” 
membrane, which bounds it (PI. IV. fig. 4, ptn.). This cavity does not possess openings 
which communicate directly with the outside, as is the case with the cavity (coeloma) of 
Nautilus. The orifices observed in the Challenger Spirula (PI. IY. fig. 2, ab ; fig. 4, 
b ; fig. 5, w') have been recognised as being produced artificially. 
V/lll 
Fig. R.—Pallial cavity of Spirula reticulata, 
laid open, all the nidamental glands re¬ 
moved, ventral view; x 4. i, gill ; ii, 
kidney; iii, ink bag ; iv, shell; v, eggs 
in the oviduct; vi, oviducal gland ; vii, 
aperture of the oviduct; viii, anus; ix, 
external renal orifice. 
Fig. S.—Ventral view of . the renal organs of Spirula reticulata ; x 8. i, 
gill ; ii, branchio-cardiac vessel; iii, appendage of the branchial heart ; 
iv, spongy body of the kidney ; v, ventricle; vi, abdominal vein ; 
vii, branchial heart; viii, posterior pallial vein ; ix, afferent branchial 
vessel; x, point where the reno-pericardial duct opens ; xi, junction of 
the two visceral nerves; xii, visceral nerve ; xiii, vena cava ; xiv, 
branchial nerve ; xv, external aperture of the kidney. 
The kidneys are found behind the nidamental glands on each side of the rectum, at 
the ventral surface of the visceral sac (Fig. R, ii). They are almost triangular in form 
and have no communication with each other. 1 
The vena cava, as we have seen above, is divided at the back of the anus into two 
branches directed backwards ; each one passes into a renal sac, and, joining the correspond¬ 
ing abdominal vein, form with it the afferent branchial vessel ; the whole portion of 
1 Contrary to what Owen says, who speaks of a single renal sac (Ann. Mar/. Nat. Hist., ser. 5, vol. iii. 
p. 11). 
(ZOOL. CHALL. EXP.—PART LXXXIII.— 1894.) 
4 
