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end in rounded extremities. It thinly coats the intestine, and 
opens by two ducts into the stomach. 
Overlying the liver, and burrowed into by the reproductive 
organs, is a ductless glandular mass, permeated by blood-chan- 
nels, which may “act,” as Mr. Hancock says, “as a sort of 
packing” (like Paley’s spleen?) “to these organs.” Its vesicles 
may also aid the heart “ by their resiliency when the mass is 
gorged with blood.” 
The two sexes are combined in one individual. Though 
separate organs a^’e devoted to the secretion of the male and 
female elements, they are associated in one mass, reminding 
us of the so-called “ ovo-testis,” which occupies the last whorl of 
the liver in Gasteropods (e.g. snails and slugs). Their ducts, 
which are distinct, follow the curvature of the last loop of the 
intestine, and terminate at the atrium, by the side of the anus 
{gr and ov, fig. 10). The ova are prolDably impregnated in the 
“ cloaca” — that portion of the atrium into which the generative 
ducts and anus open. In each is developed a tadpole-like 
embryo (fig. 12), which is hatched about thirty hours after 
fecundation. The fore part of this tadpole — as we may term it 
— is furnished with three sucker-like projections. By these it 
attaches itself to some suitable spot before undergoing subsequent 
changes. A pigment spot may also be seen in the middle line 
of the back, and a second one laterally (fig. 12 e). These were 
at first supposed to be eyes ; but Krohn, from his observations, 
considers this not proven. They persist for a long time after 
larval existence, but, after fusing into a single mass, finally dis- 
appear. The tail of the larva, after being retracted into the 
interior of the now attached body, where it is rolled up into a 
spiral coil, breaks up eventually into a lobular mass, and becomes 
no longer visible. A cylindrical axis has been lately discovered 
in the larval tail, resembling in structure the noto chord of the 
lancejet {Amjjhioxus), the lowest of the fishes. It is significant 
that the late Professor Goodsir pointed out the likeness between 
the enormously dilated, ciliated, and perforated pharynx of this 
very fish and the gill-sac of the Ascidian. 
The nerve system is very rudimentary, there being^but one 
ganglion, situated betwixt the inhalent and exhalent orifices, 
and lying between the mantle and lining membrane. From it 
radiate a few nerves to the respiratory tubes and mantle, and to 
the “ branchial tubercle,” a supposed organ of special sense 
(taste or smell ?) which lies immediately in front of the upper 
end of the oral lamina. 
We will now pass on to a brief survey of the erratic Tunicata, 
taking the Safjjidw as representatives of this division. 
These animals are of especial interest to the naturalist, seeing 
