REPORT OX THE PTEROPODA. 
15 
The Generative Organs . — The genital gland (PL II. fig. 1, Jc) occupies the posterior 
part of the visceral mass. The duct (/) issues from it dorsally, passes to the left side of 
the alimentary canal and then to its ventral surface, and terminates by opening at the 
right side of the cephalic mass (o). 
At the distal extremity of the genital duct are situated the accessory genital glands 
(PI. II. fig. 1, m). In Clio ( Creseis ) acicula I have sought in vain for the receptaculum 
seminis with a long duct, figured by Gegenbaur. 1 In Styliola only the receptaculum 
S'- minis is a little elongated. Generally ( Creseis , Hyalocylix) there is a swelling (pro- 
bably glandular) near the origin of the genital duct. 
The genital aperture is connected by a ciliated spermatic groove with the orifice of 
the penis (PI. II. fig. 1, q), which is placed as in Limacina. 
The Xervous System. — In all species of Clio the cerebral and pedal ganglia agree in 
structure and position with those of Limacina. 
If the nervous system of Clio be examined by a series of transverse sections, it is 
found (PI. II. fig. 9) that though each cerebral ganglion is outwardly single, yet it con- 
tains two distinct centres ; the pleural ganglion (5) is fused with the cerebral ganglion 
proper (a), and is not recognisable on superficial examination. The same is the case in 
all Thecosomata, except as we shall see in Cuvierina, in which the pleural ganglion is just 
noticeable externally. 
In Clio, as in all the other Cavoliniidse, the ganglionic elements of the visceral com- 
missure do not form a bilaterally symmetrical mass as has been usually represented, and 
as indeed I myself have previously figured in a somewhat diagrammatic sketch of the 
central nervous system of Cavolinia } 
The left half of the visceral ganglionic mass is always larger than the right ; and in 
the case of Clio this is particularly prominent in the subgenus Creseis. This shows 
clearly that, as in Limacina, the ganglion called “abdominal” is fused with one of the 
anterior visceral ganglia (in all the Cavoliniidse this is the subintestinal), for the visceral 
nerves (that is to say, those of the abdominal ganglion, viz., the visceral nerve supplying 
the heart and the kidney, and the genital nerve) and the left pallial nerve issue from 
the left portion of the visceral ganglionic mass, whilst from the right half of this mass 
there issues only the right pallial nerve, which supplies the right half of the mantle and 
the osphradium. 
The description given by Stuart 3 of the nervous system of Clio ( Creseis ) acicula is 
so strange and inaccurate that it would require too long to attempt to correct it here. 
The enteric or stomato-gastric nervous system is composed of the same elements as 
that of Limacina, and only differs from it in the fact that the two buccal ganglia are 
approximated to each other instead of being separated and joined by a commissure. 
1 Untersuchungen tiber Pteropoden und Heteropod en, pi. ii. iig. 3, c, d. 
2 Recherches sur le systeme nerveux des Pteropodes, Arcli. de Biol., t. vii. pi. iv. fig. 11. 
3 Ueber das Nervensystem von Creseis acicula, Zeitschr. f. wiss. Zool., Bd. xxi. pi. xxiv. a. 
