_PROTOZOA. 79 
wonderful regularity of structure. Their forms are extremely various, 
the species being very numerous. Some are simple, and of these some 

Fig. 63.—Foraminifera : 
1—7, Various species; 8, Part of two chambers of one; 9, Vertical Section of a fossil species. 
are ‘orbicular, others curiously flask-shaped ; but many. are chambered, 
and thus composed of parts variously arranged, sometimes in a straight 
line, sometimes spirally, but‘always regularly. These chambered shells 
seem to be formed in consequence of what is called gemmation,} or the 
growth of new individuals from an existing animal, as of buds on a tree. 
The shells of all the Foraminifera are pierced with numerous pores, 
through which long delicate processes—extensions of the soft body of the 
animal—are protruded when occasion requires. 
‘Sponges.—Sponges, the only Protozoa that attain a large size—which 
they do, however, merely in virtue of the formation of aggregate or 
compound animals by gemmation—are perhaps the lowest of all creatures 
in the scale of animal life. The movements of a living sponge suggest the 
idea of animal rather than of vegetable life, but its form and manner of 
growth are plant-like. It is fixed by its base like a sea-weed; it seems 
utterly insensible to touch ; it may even be pinched with a forceps, or 
torn to pieces, or bored with a hot iron, without a symptom of suffering. 
No wonder, therefore, that sponges should long have been regarded as 
plants. When the life-history of a sponge, however, is considered, its 
animal nature at once becomes certain. A sponge in its mature state 
generally consists of a horny fibrous framework, which is all we see in the 
+ From Latin, gemma, a bud. 
