556 RHIZOPODA ; FOR AM IN IF ERA. 



jelly advances slowly by their agency in any required direction. 

 In feeding, the Amcp.ba, destitute of a mouth, attaches itselt 

 to the body which it is desirous of appropriating, and by the 

 slow extension of its substance gradually envelopes the morsel 

 of food, which is often so large that the gelatinous matter of the 

 Amceba only forms a thin coat over it. In some allied species, 

 such as Actinophrys, the processes thrown out are delicate fila- 

 ments, and these appear to have the power of adhering firmly to 

 any passing Animalcule, which is speedily drawn down to the 

 surface of the gelatinous body of the Rhizopod, and enveloped by 

 it in the manner above described. Some other fresh-water 

 Rhizopoda have the power of secreting a little horny shell, which 

 serves for the protection of the animal, leaving a small aperture 

 at one extremity for the protrusion of the gelatinous processes 

 or filaments. 



1221. The marine forms are "generally compound, a number 

 of these delicate gelatinous creatures being intimately associated 

 together. They are always inclosed in delicate calcareous shells, 

 divided into chambers corresponding in number with the indi- 

 vidual Rhizopods of which the colony is composed ; from the 

 strong resemblance which some of them bear to the chambered 

 shells of some Cephalopoda ( 976), they have been supposed to be 

 formed by animals of that class. Many kinds of them exist on 

 almost every sandy shore ; but their extreme minuteness causes 

 them to be usually overlooked, and is also an obstacle to the 

 satisfactory determination of the character of the animals which 

 construct them. By D'Orbigny, who first attracted the atten- 

 tion of Naturalists to the details of this curious group, it was 

 regarded as an Order of Cephalopoda ; and he gave to it the 

 name of Foraminifera, on account of the communication 

 between the chambers not being established by one principal 

 tubular aperture, the siphuncle, but by numerous minute 

 foramina or porous orifices. The species which exist on the 

 shores of Northern Europe are so minute, as not to be easily 

 examined, even with the microscope ; but those which are found 

 in the Adriatic Sea are sufficiently large to be recognised with 

 the naked eye. 



