. Amphioxus e le origini dei vertebrati [microformati]. Vertebrati; Chordata; Pesci; Ascidiacei; Vertébrés; Cordés; Poissons; Ascidiacés. ho'ili .%: •!", 140 DEVELOrMKXT AM PHI OX CS. zioni di esse sono visibili da questo lato. In alcune delle feritoie secondario il margine dorsale, che in precedenza aveva cominciato a curvarsi verso il basso, ha ora raggiunto il margine ventrale e fuse con esso (Fig. 78, terza fenditura secondaria). In questo modo è la lingua-bar formate e il modo primitivo semplice gill-apertura è diviso in due metà distinte. La formazione della lingua-bar si verifica nelle feritoie secondario cons

• Collaboratore: Library Book Collection / Alamy Foto Stock
• ID dell’immagine: RJ26GD
• Dimensioni dei file: 7,1 MB (222,6 KB Download compresso)
• Liberatorie: Modello - no | Proprietà - no
• Dimensioni: 972 x 2571 px | 8,2 x 21,8 cm | 3,2 x 8,6 inches | 300dpi

Altre informazioni

Questa foto è un'immagine di pubblico dominio, il che significa che il copyright è scaduto o che il titolare del copyright ha rinunciato a tale diritto. Alamy addebita un costo per l'accesso alla copia ad alta risoluzione dell'immagine.

Questa immagine potrebbe avere delle imperfezioni perché è storica o di reportage.

. Amphioxus and the ancestry of the vertebrates [microform]. Vertebrates; Chordata; Fishes; Ascidiacea; Vertébrés; Cordés; Poissons; Ascidiacés. i'ili .%: •!, ' 140 DEVELOrMKXT OF AM PHI OX CS. tions of them are visible from this side. In some of the secondary slits the dorsal margin, which had previously begun to curve downwards, has now reached the ventral margin and fused with it (Fig. 78, third secondary slit). In this way is the tongue-bar formed, and the primitively simple gill-opening is divided into two distinct halves. The formation of the tongue-bars occurs in the secondary slits considerably in advance of the primary, both actually and relatively, since the latter have existed all through the earlier period of the larval development without a trace of tongue-bars. PcripJiaryngeal Ba?ids. The endostyle has now grown a long distance behind the club-shaped gland, and extends backwards between the two rows of slits as far as the middle of the second secondary slit. From the anterior part of the upper half of the endostyle, which is now nearly equal in length to the lower half, arises an epithelial tract in the wall of the pharynx, which appears in the form of a band of ciliated cells, and proceeds backwards below the notochord to the end of the pharynx. A corresponding ciliated band occurs in the left wall of the pharynx, proceeding from a similar point in the. lower limb of the endostyle. In their course below the notochord the two bands take part in forming the hyperpharyngeal (dorsal) groove of the pharynx. Atrophy of First Primary Gill-slit and Club-shaped Gland, etc. We have already seen indications of a reduction in the size of the first primary slit. This reduction has advanced considerably in the stage we are now describing (Fig. 78), where the slit in question is only recognisable in side view as a small groove.. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloratio

Parole chiave associate all'immagine

• bookcentury1800
• bookdecade1890
• booksubjectfishes
• bookyear1894