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POPULAR SCIENCE REVIEW. 
The same animals seem, moreover, to have formed a not un- 
important item in the “ Materia Medica ” of the Komans ; for 
Pliny writes : — Tethea torminibus et inflationibiis occurrunt. 
Inveniiintur hsec in foliis marinis sugentia, fungorum verius 
generis quam piscium. Eadern et tenesmum dissolvunt re- 
numque vitia.” * 
The Tunicates well illustrate what Darwin has so aptly 
termed “The Imperfection of the Greological Kecord,” for no 
remains which can with certainty be referred to this group — 
which might be expected, from their lack of a calcareous shell 
— have yet been discovered in any formation. 
EXPLANATION OF PLATE XLVU.f 
Fig. 1. Boltenia (from the educational series in the Museum of the lloyal 
College of Surgeons). A vertical section has been made through 
the test, which has internally a cartilaginous appearance. Lying 
free in the exposed cavity is the body of the animal, invested 
with the muscular mantle. Glass rods are inserted into the 
orifices of entrance and exit. 
„ 2. Portion of gill-sac of Ascidia Parallelogramma, highly magnifi.ed. 
After Alder. 
„ o. Clavelina p'oducta, natural size. After Milne-Edwards. 
„ 4. Cones of gill-sac of MoJgida arenosa, seen in profilq, highly magni- 
fied. After Alder. 
„ 5. Clavelina lepadiformis^ natural size. After Mihie-Edwards. 
,, G. Botnjllus bivittatus, on a piece of sea- weed. Natural size. After 
Milne-Edwards. 
„ 7. The same species, magnified. After Milne-Edwards. 
„ 8. Byrosoma. From the educational series, Eoyal College of 
Surgeons. 
„ 9. Ajjpcndicularia Flagellum, highly magnified. After Huxley. The 
letters N S indicate a scale of the natural size of the animal. 
„ 10. Phallusia nigra, from a Hunterian specimen. Royal College of 
Surgeons. One side of the test, mantle, and gill-sac has been 
removed, in order to display the digestive tract and the organs 
of reproduction in situ. 
* Faturalis Ilistoria. lib. xxxii. Gl. 
t Through the courtesy and kindness of Mr. W. II. Flower, F.R.S., Con- 
senator of the Museum of the Royal College of Surgeons, permission was 
gained from tlie Museum Committee to make drawings from preparations 
contained in the Museum of the College. 
"NVe are also greatly indebted to Mr. Charles Robertson, Demonstrator of 
Anatomy at the University Mu.seum, Oxford, for some magnificent specimens 
of Ascidia Arachnoidea, by the aid of which the memory has been refreshed 
on several important points. 
