A treatise on zoology . y larger brachioles, arising inthe immediate neighbourhood of the mouth. At the same time, a difference manifests itself in the structureof the thecal plates. From the indefinite relations of stereom andstroma noticed in earlier Amphoridea arise two types of structure(Fig. I.). The canals traversing the stereom, more or less per-pendicularly to the thecal surface, either cease to be simple( haplopores ) and become connected in pairs ( diplopores ) stillperpendicular to the surface ; or they come to lie parallel to the sur-face and at right angles to the sutures. In the
A treatise on zoology . y larger brachioles, arising inthe immediate neighbourhood of the mouth. At the same time, a difference manifests itself in the structureof the thecal plates. From the indefinite relations of stereom andstroma noticed in earlier Amphoridea arise two types of structure(Fig. I.). The canals traversing the stereom, more or less per-pendicularly to the thecal surface, either cease to be simple( haplopores ) and become connected in pairs ( diplopores ) stillperpendicular to the surface ; or they come to lie parallel to the sur-face and at right angles to the sutures. In the latter case we may 42 THE CYSTIDEA suppose that the canals represent stroma strands continuousacross the sutures; those crossing any one suture come to occupya rhombic area bisected by the suture-line, and, since, in weatheredplates, there appear to be pores at the ends of these canals, theareas have been called pore-rhombs {Poren-roMten, see Fig. XY.,Echinosphaera, and XVI., Orocystis). There also takes place a gradual. Ilii. I. Htriirturft of the Ust in AristocyHtidac. 1, jiliito of A ristoeystis hohcminis showing liaplopores,some of which an coiinnctfd i)y a horsn-shoo ciiiKil, x 4 ; 2, portion of saiuo furtlit-r cnhirjjtHl ; 8,portions of Hurfacti of otluT ., Kfidiialiy Icidiiin up to such n structure as in 4, a plateof flUix SMijirirld, with (iii)loporcs ; T), a (iiploiiorc of rather (litffiriit form ; (5, section of a(lipiopofH ; th» hypostt-rtoni is shown, hut tlie fpislfnoni, if there were any, is removed ; 7, anatural replacement (l»y inliltration of mineral matter) of the ori>;inal stroma-strands andsutures in plates of tulii (y), the stereom dissolved away ; S, plates of Aristm-iistia in similarcondition snowing verti<al strands (^hapiopons) in the middle, and radialiiij; strands at thesutures. All hnurts enlarged. (1, J, 3, and s after Marrande ; 4 and 7 after Itnuault.) increase in the aiua, and a decrease in the number, of the thecalplates rela
Size: 1521px × 1643px
Photo credit: © The Reading Room / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookcentury1900, bookdecade1900, bookpublishe, booksubjectzoology
