. A textbook of invertebrate morphology [microform]. Invertebrates; Morphology (Animals); Invertébrés; Morphologie (Animaux). 16 JNVERTEBRATE MORPHOLOG T. XJ^K. Fig. 4.âArcella mitrata (after Leiuy) masses of protoplasm coutaiuiDg a nucleuf? and a contractile vesicle and presenting a slight differentiation into a peripheral more transparent ectoplasm and a central more granular eiidoplasm in which the nucleus is imbedded. The pseudo- podia are as a rule blunt loV)ose processes, though in some species they are more or less fila- mentous and may even be some- what permanent. The majority of fo
. A textbook of invertebrate morphology [microform]. Invertebrates; Morphology (Animals); Invertébrés; Morphologie (Animaux). 16 JNVERTEBRATE MORPHOLOG T. XJ^K. Fig. 4.âArcella mitrata (after Leiuy) masses of protoplasm coutaiuiDg a nucleuf? and a contractile vesicle and presenting a slight differentiation into a peripheral more transparent ectoplasm and a central more granular eiidoplasm in which the nucleus is imbedded. The pseudo- podia are as a rule blunt loV)ose processes, though in some species they are more or less fila- mentous and may even be some- what permanent. The majority of forms, however, secrete a protective shell of varyiiig composition and com]^lexity. In Arcella (Fig. 4) it is chitinous and smooth, and len- ticular in shape, completely sur- rounding the protoplasm, the pseu- dopodia projecting from the cir- cular opening on the flat surface; in Eughjpha it is similar in composition, but sculptured on the convex surface ; in Dijffugia the shell is flask-shaped and composed of particles of sand and similar foreign bodies cemented together, while in a large number of forms, es- pecially those which are marine in habitat, the shell is calcareous in composition. It is in these forms with calcareous shells that the great- est complexity of structure occurs. In some, such as Gromia, the shell is simple and flask shaped, the protoi'lasm pro- truding from the mouth of the shell and covering its entire surface as a delicate layer, from whi'*h ilie long, slender, and fre([uently anastomosing pseud()))odia take their origin. Al- though tlie ]iseudopodia are practically permanent in form their protoplasm is continually changing, carreuts streaming from the body towards the tii)S of the pseudopodia and re- turning again to tlu^ central mass, a constant circulation beiii}^ thus maintained, and food-](articles caught by the delicato pseudopodia conveyed to the central mass, there to bo di- gested. A simple shell is, however, comparatively raro among these
Size: 1378px × 1814px
Photo credit: © The Book Worm / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookcentury1800, bookdecade1890, bookpublishernewyo, bookyear1896
