312 
THE OCEAN WORLD. 
organs of sensation present themselves in a very rudimentary fashion- 
We find eyes, and, after very minute search, a single ear has been 
found. They are propagated by budding, and also from eggs. The 
young are subject to some very curious metamorphoses, some parti- 
culars of which will be given farther on. 
The Tunicata are divided into Asciclia and Salpa, to which som e 
naturalists add the Brachiopoda. 
Ascidians. 
The Asciclia, from the Greek word da^cBiov, leather bottle, have, 
the name indicates, the shape of a bottle or purse. The analogy becomes 
Fig. 124. Asciditi microcosmus (Cuvier). 
more evident when it is considered that these creatures are habitually 
filled with water, which can be expelled by very slight pressure. 
The Ascidians are sometimes frQe, sometimes united to others m 
manner more or less intimate. Hence their division into the three 
groups of simple, social, and composite Ascidians. 
Simple Ascidians attach themselves, each individual singly, to ro< ' 
and other submarine bodies, and generally at a fixed depth. Asci > 
microcosmus, a Mediterranean species, represented in Fig. 124, nutf 
be quoted as a type of this division of Ascidians. The vulgar nai» e 
of Cynthia, or the little world, is probably given from its being 
habited by quite an animated colony of algae and poly piers, which dive 
