ZOOLOGY. 



The Atnaeba, or Proteus animalcule, so called 

 from the facility with 

 which it can change its 

 shape, possesses a nu- 

 cleus and contractile ves- 

 icle, and its pseudo-podia 

 are blunt and club-shaped, 

 but they do not flow to- 

 gether. 



The Foraminifera have 

 a calcareous ' test,' perfor- 

 ated by numerous small 

 apertures, through which 

 pseudo-podia are emitted, 

 or a test made up of sand 

 grains cemented together, 

 and leaving openings for 

 the ' false feet.' Some are 

 simple, as Lagena, but 

 most are composite, pro- 

 duced by continuous gem- 

 mation or budding, each 

 to the body by which it 

 bud remaining attached 

 was put forth. Some 

 shells have only a single aperture placed at one 

 end,' through which the pseudo-podia are pro- 

 truded. According to the plan of this budding, 

 so will be the form of the composite body pro- 

 duced. In some, the parts are arranged in a 



Foraminifera 

 Gromia. 



Foraminifera : 

 i. Lagena striata ; 2. Textilaria ; 3. Operculina. 



straight row ; in others, a single row is rolled into 

 a spiral; and in some the parts are in the same 

 plane, or they may form a spire, with a more 

 or less conical form, the first chamber being 

 at the apex. All the chambers com- 

 municate together by openings between 

 adjacent chambers. They are marine, 

 and exist in enormous quantities in the 

 bed of the Atlantic, forming the chief 

 part of the ' ooze,' which is composed 

 almost entirely of a species of Glob- 

 igerina (G. bulloides}. 



The Polycistince have a silicious 

 instead of a calcareous shell, which is 

 Podocyrtis. often most beautifully sculptured. They 

 are all minute, and are frequently found 

 in infinite multitudes, forming a coloured cloud 

 on the surface of the sea. 



CLASS III. GREGARINIDiE 



are parasitic in the intestines of some insects, 

 and in the earth-worm. They are probably more 

 allied to some low forms of Entozoa than to the 

 Protozoa. 



CLASS IV. PORIFERA OR SPONGIDEA. 



In the sponges, the Protozoa attain their largest 

 dimensions, and their greatest prominence in the 

 economy of the present time. The body consists 

 of sarcode, which is supported by an internal 

 skeleton or framework composed of carbonate of 

 lime, of silica, or of horn, or of a combination of 

 one of the former two with the latter. In the 

 bath sponge, which is the best known example, 

 the skeleton consists of a network of flexible horny 

 fibres alone. When the sponge is taken living 

 from the sea, it is completely filled and covered 

 with the jelly-like living matter. A thin gelat- 

 inous membrane, perforated with very small holes, 

 covers the surface, and every here and there rises 

 into a papilla with a large hole at the top. These 

 larger openings are called oscula, and they open 

 into a set of channels which divide and branch 

 till they penetrate through the entire substance of 

 the sponge. The pores in the outer wall likewise 

 communicate with the ultimate meshwork of the 

 sponge, and are thus in communication with the 

 channels and the oscula. The channels are lined 

 with cilia delicate hairs, which, by a perpetual 

 lashing movement, drive the water along the 

 channels ; or they have somewhere in their course 

 chambers lined with cilia. The nutrition and res- 

 piration of the sponge are thus conducted : water, 

 with organic food in 

 solution or suspension, 

 and containing air, 

 enters the pores, 

 passes through the 

 tissue of the sponge, 

 and is exhausted by 

 the absorbing sarcode 

 surface. The effete 

 water is then col- 

 lected into the chan- 

 nels, and urged for- 

 ward by the cilia till 

 it pours out at the 

 oscula in a stream. 

 True sexual reproduc- 

 tion has not yet been 

 established for spon- 

 ges : they multiply by 

 the separation of small, 

 oval, ciliated buds, 

 called gemmules, 

 which escape along 

 with the water from 

 the oscula. 



The principal orders 

 of the Porifera are the 

 Calcispongias, the 

 Hexactinellidae, the 

 Ceratospongias, the 

 Corticatae, and the 

 Halichondrias. 



In the Calcispongice 

 (calx, lime, and spog- 

 gos, a sponge), the 

 sarcode is supported 

 by granular horny 

 matter, mixed with 

 three - rayed needles Hyalonema. 



or spicules of carbon- 

 ate of lime. These sponges are found frequently 



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