246 MR. J. D. MACDONALD ON THE ANATOMY OF EURYBIA GAUDICHAUDI. 
is beset with large hepatic lobuli containing cells distended with rich brown-red, yellow, 
and green fatty globules, imparting to them a beautifully variegated appearance. No 
gastric plates or teeth are visible, though universally present in the true Thecosomata, 
- Having left the stomach, the intestine soon curves forwards to terminate anteriorly near 
the generative openings, on the right side of the body. 
The salivary secretion is furnished by two irregularly lobulated organs, lined with rather 
large secreting cells, and lying one on either side of the cesophagus as it emerges from the 
buccal mass. 
The heart occupies an antero-dorsal position, and its long axis appears to lie transversely; 
but I have not been able to detect a respiratory organ, or even the actual distribution of 
the blood-vessels. _ 
The main centres of the nervous system are the subæsophageal ganglia, which are well 
developed, and support the auditory capsules containing vibrating otokonia on their 
inferior surface. 
The ovarium consists of a fan-like expansion of lobuli, on the borders and extremities 
of which the ova are clustered within the enveloping sheath. From this expansion a 
number of tubuli arise, and ultimately unite to form a wide oviduct distinguished from 
the spermatic duct and intestine by the large longitudinal and nucleated fibres of its mus- 
cular coat. A large cecal appendage, distended with a bright-orange and plastic fluid, 
appears to open by a short duct at the same external orifice. This organ is probably the 
homologue of the so-called spermatheca of the Pulmoniferous Gasteropods ; and its con- 
tained fluid offers a remarkable analogy to that occurring in the ovarian sac of some 
Cephalopods. 
The lobuli of the testis lie upon and coincide so closely with those of the ovarium, that 
it is difficult to distinguish them; but the stout vas deferens, arising from the point at 
which the divisions converge, soon communicates, above and a little to the right of the 
ovary, with a spheroidal sac or vesicula seminalis, which may be readily seen from 
without, through the cartilaginous mantle. The spermatic duct thence proceeds forwards 
in company with the oviduct, and enters the neck of the external male organ, to termi- 
nate in a perforated dart or rigid point, which occupies the fundus of the inner protrusible 
membrane of a double-walled pyriform sac having an external orifice near that of the 
oviduct, on the right side, behind the corresponding swimming-fin. 
The spermatozoa of this Pteropod are remarkable for their great length and peculiar 
looping and spirally twisting movements, as illustrated in Pl. XLIII. fig. 8 Bd. The fila- 
ments appear to rotate on their long axes, and twirl up, like an over-spun thread unlay 
themselves, and twist up again, with wonderful rapidity while their activity lasts. —— 
Eurybia 18 ovo-viviparous; and the development of the young may be studied with 
much interest While yet within the body of the parent. The simple capsule of the ovum 
zum: ‚little for remark ; but the ineluded embryo in the comparatively advanced stage 
n my points of analogy to that of an ordinary Gasteropod. : It 
‘ e incipient cartilaginous mantle is of large size compared with the embryo itself. 
is globose in figure, with an opening at one end, through which the ciliated vela of the 
young Eurybia may be seen protruding. These latter organs form expanded lobes, lying 
