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rorULAR SCIENCE REVIEW. 
The Ascidia proper comprise — 
a. Those which are isolated, e.g. Boltenia and Phallusia 
(figs. 1 and 10 ) — Compound Ascidians. 
fS- Those connected by stolons” — trailing prolongations 
like the “runners” of strawberry-plants — into which blood- 
channels are continued, e.g. Clavelina {fig. 5) — Social Ascidians. 
7 . Those in which the tests are fused into a common gela- 
tinous mass, in which the individuals are imbedded in groups, 
frequently star-like, e.g. Botryllus (figs. 6 , l)^Gompound 
Ascidians. 
The oceanic members not yet mentioned are, Pyrosoma, 
Doiiolum, and Appendicularia. The Pyrosomata are elo- 
quently described by Professor Huxley as “ miniature pillars of 
fire gleaming out of the dark sea, with an ever-waning, ever- 
brightening, soft bluish light, as far as the eye could reach on 
every side.” 
To speak more prosaically, each animal consists of a hollow 
cylinder, closed at one end, open at the other, somewhat like a 
test-tube (fig. 8 ). At the open end is a kind of valve. In the 
walls a number of zooids are imbedded perpendicular to the axis 
of the tube, whose anterior orifices look outwards, while the 
posterior open into the interior of the cylinder. 
The cylinder moves by the reaction of forced-out water 
against its closed extremity. 
Keproduction takes place in two ways ; both by an asexual 
budding, and by impregnated ova, each of which gives origin 
to four aggregated zooids. 
Doiiolum, as its name implies, is cask-shaped.* Both ends 
are open, the hinder being fringed. The gill is represented by 
two bands (“epi-” and “ hypo-pharyngeal ” of Huxley, respec- 
tively) which are connected by transverse bars. 
Appendicularia (fig. 9), a minute animal, is the lowest form 
of Tunicate. In it the larval tail is persistent, while the gill is 
entirely absent. There is, however, a “ ciliated band” on the 
ventral surface of the respiratory cavity. Appendicularia 
differs from all other Tunicates in having no reversal of the 
blood-current, and in possessing individuals of separate sex, of 
which, however, the male only has at present been discovered. 
Prfjfessor Huxley divides the Tunicata {Ascidioida) into 
three orders — 
1 . Brancldalia, in wliich the gill-sac is so large that the 
digestive and generative organs are pushed to one side of it. 
The solitary Ascidians, Boimyllus, Salpa, and Pyrosoma, belong 
to this order. 
2 . Ahdominalia, in which tlie gill-sac, being comparatively 
Diminutive of Lat. dolium, a cask. 
