530 Mr. W.S. MacrEAY's Anatomical Observations 
Tethya of Aristotle, or les Ascidiens of Savigny, I cannot do bet- 
ter than cite the description given by the ancient philosopher, 
and mentioned above. | 
In his Historia Animalium, under the head of 'l'estaceous Ani- 
mals (và orreuzódseua), he observes that ** there are some, such as 
those called T74ve, which are so entirely surrounded by their test 
or envelope* as to have no part of their flesh exposed." So far 
this accurate and philosophically drawn character may apply to 
the whole of the Tunicata: but Aristotle afterwards proceeds to 
describe the Tethya in the following more definite terms. ** But 
of all these animals (viz. ra oorguncdegue), those which are called 
Tethyat have the most remarkable nature: for with them alone 
is the body entirely concealed in the test. This test or envelope t 
(và corgaxov) is between the texture of leather and shell, and may 
consequently be cut like a piece of tough hide. The animal 
adheres to the rocks by its test, and has two passages or ori- 
fices (régous), distant from each other, and so small as not to be 
easily visible. By means of these it imbibes and discharges the 
water. 
** On opening one of these animals, the inside presents, in the 
first place, a membrane composed as it were of nervures§ (mére 
* "Kori D à Gha mepityeras TG ÓcTQdxdo xal o002y ris cagnds Exes elg TÒ tho yumvov, oloy 
ra xaAobpsyx Thiva. 
+ As Aristotle afterwards mentions the colours of such species of Tethya as he was 
acquainted with, it seems probable that his species were the Ascidia microcosmus Cuv. 
and Ascidia papillosa Linn. 
+ In the original, ** 72 9 dorpandy tors werakd déguaros xai éorpaxou.” This passage is 
curious, as showing Aristotle’s disposition to generalize; a disposition so rare among 
modern comparative anatomists, that we need not be surprised at observing some of 
them to be perfectly ignorant of Natural History. 
§ This is a good description of the beautifully reticulated membrane which forms 
the branchiz of the Tethya, and will be easily understood on referring to the dissection 
of Dendrodoa glandaria, as given Pl. XX. fig. 5. Aristotle appears, however, by some 
mistake to have considered the branchial pouch as surrounding the intestine. 
veveadn), 
