where in the sea, attached to all sorts of fixed or 
movable objects; rocks, ship-keels &c. It used 
formerly to be imagined that the 
Barnacle Goose was developed from 
this creature. 
The species belonging to the 
Balanideé are fixed without a stalk. 
Balanus tintinnabulum, fig.q, is found 
in abundance attached to ships re- 
turning from the Southern Seas ; 
and Coronula balenaris, both surfaces 
of the shell of which are represented at fig. r 1 & 2, 
is parasitic on the skin of the whale. 

Nauplius 
Larva of Lefas 
anatifera. 
49 

Suborder H. Rhizocephatla. 
These animals are degraded to the utmost by 
parasitism. Those of the genus Fe/fogaster lose the 
segmentation of the body, the organs of sense, the 
limbs, and even the cavities of the mouth and the 
intestine, and become a mere tube attached to the 
abdomen of the Decapoda, while they absorb its 
juices by root-like threads. Here, too, the initial 
Nauphus form indicates the real affinities of the 
animal. A creature of the degraded type just de- 
scribed is represented at Fig. s (Sacculina carcini). 
Subkingdom Mollusca. 
I. Tunieata, 
Plate XXII (left side). 
These are marine animals of a bag-like or 
barrel-like shape. 
often transparent bag contains a 
suspended in it, with a thinner integument, containing 
the organs of the animal. At each of the two points 
The leathery or cartilaginous and 
second loosely 
where the inner bag is connected with the outer, 
there is an opening to admit of a current of water. 
These creatures are hermaphrodite, and often pass 
through a rather complicated metamorphosis. 
Class I. Thaliacea. 
Freely swimming species of baglike ‘or barrel- 
like form, with a transparent outer covering. The 
two openings of the mantle are close together. Some | 
are found swimming freely in the open sea, and 
others are found linked together in chains; and yet 
both forms belong to the same species. The chain- 
like animals produce young which swim freely about. 
Some reproduce their kind asexually by budding, 
and form new animals which remain linked together 
into chains; and then lay eggs again. This kind of 
reproduction is called alternation of generations. 
Such a chain is shown at Fig. n, which represents 
Salpa zonaria. 
Class I. Ascidia. 
Most of these animals are bag-like in form, 
and the two openings of the mantle lie close to- 
gether. Their development is very interesting, for 
they possess an organ, the spinal cord, which occurs 
elsewhere only in Vertebrata. 
Fig. 0. Cynthia ramus is a species which often 
founds colonies, and becomes a compound ascidian. 
Sometimes the colonies become spongelike and over- 
grow foreign substances like a crust, and some ex- 
hibit the form of a hollow fir-cone, on the outside 
of which the separate animals are placed. 
Fig. p. Pyrosoma atlanticum is one of the latter. 
It swims freely in the sea, emitting a beautiful light, 
and is one of the numerous animals which occasion 
the luminority of the sea. 
II. Mollusca (typical). 
In the numerous animals 
under this heading, the body is unjointed, and there 
are no limbs. They are enabled to move by means 
of a powerful muscle on the abdominal surface of 
the body, called the foot. There is no movable 
skeleton, either external or internal, but there is 
generally a calcareous shell formed of one or two 
parts, which quite encompasses the body. In the 
higher Mollusca the front part of the body forms a 
more or less distinct head, which in one class is 
Amphibia &c. 
properly included 

surrounded by a fringe of arms. There is a nervous 
system, in addition to well-developed organs of sense. 
The intestine is divided into several sections, and 
there is a plate in the mouth-cavity set with delicate 
teeth. They 
are sometimes separate, and sometimes the animals 
The species are mostly aquatic 
generally breathe with gills. The sexes 
are hermaphrodite. 
(in general, marine) and even the land-moluscs preter 
damp places. 
The Mollusca are divided as follows: 
