THE RHIZOPODS. 593 
Order II., StrtcorpEa, includes the highest of the class. The skeleton framework of these 
Sponges is almost wholly made up of silicious spicules. The Zethia and Geodia are promi- 
nent forms. 
What are known as Glass Sponges are of this Order. 
The Hyalonema, or Glass-rope Sponge, is found in the waters around the Philippine 
Islands. Though so much in appearance like spun glass, it is nevertheless of horn, like the 
nails and hoofs of animals. When burnt it has the same odor as horn. In 1860 naturalists 
first found the true nature of these objects ; they, 
as well as the glass vases, were so artificial in 
appearance that they were taken as objects made 
up for a market. 
The Holtenia carpenteria, seen in the engray- 
ing, is another of different shape. Of all, for beauty 
and singularity, the Huplectella, or Glass Vase— 
Venus-cup—-is the most beautiful A very fine 
example is here figured. This, it will be remem- 
bered, is the framework of a Sponge, just as the 
Sponges we use are frameworks of the Sponge. 
While alive all Sponges are quite heavy, some ex- 
ceedingly so, with their flesh and the inclosed 
water. When lifted from the sea, an old black hat 
with many holes, is as good an illustration of the 
looks of a living Sponge as any. But what beauti- 
ful objects when denuded of flesh ! 
Tue editor of this edition would, as in the case 
of the Branch of the Animal Kingdom II., Porifer- 
ata, treat of the First Branch where, according to 
late authorities, it properly belongs. For classi- 
fication and nomenclature, according to modern 
authors, see tables of Smithsonian Institution. 
Branch I.—Protrozoa. First animals, is meant 
literally—or, looking at animal life in a descending 
series—the last, or lowest of animals. In our pages 
this latter view is adopted. 
The simplest object that can be called an ani- 
mal is embraced in this branch. All of this group 
can move, eat, and reproduce their kind. They 
move by little oars placed in all parts of the 
exterior ; they eat by absorbing minute animal and 
vegetable substance into all parts of their bodies ; 
and they are reproduced by the division of their 
forms indefinitely. Such creatures, we are ready 
to understand from their composition, are formed 
of single cells, whose parts are homogeneous, one a 
Z - < GLASS VASE.—Zuplectella aspergillum. (Two-thirds 
bit being a representation of another or the whole. naturallaize:) 
The Protozoa are mostly minute creatures— 
microscopic. There is some degree of rank observed among the Protozoa. The first class 
embraces the lowest, called Monera. One of these forms, called Protomyaa, is regarded as 
the simplest representative. 
The Rhizopods form a second class, but, the differences are extremely small. 
The fresh-water Rhizopods of America have been treated in a magnificent work, with 
colored plates. In the first Order of this class, the well-known Am@ba is placed. See the 
figure in accompanying engraving. 
Vou. I1.—%5. 

