. Amphioxus and the ancestry of the vertebrates [microform]. Vertebrates; Chordata; Fishes; Ascidiacea; Vertébrés; Cordés; Poissons; Ascidiacés. EXTERNAL FORM. 21 iDUs suhstan. ' pass I h roil:; epithelial a- 'ith its inapT • oral opcniii, 1 acci'uiit ()! youii- lamp: iluit the \L velar ti'ii!i\{. iccal cirri ol :. in a hackuv iense-colls. order. (Aliri \.\ of the biicc: cells bupr. lers bear sti: ic same cron;'. 5^,i:.yrJ/I Fig. 7. Velum of Amphioxus seen from (After Lankks- the inside of the pliiirynx. TKR.) Sphincter muscle of velum, Velar tentacles lying across the oral open
. Amphioxus and the ancestry of the vertebrates [microform]. Vertebrates; Chordata; Fishes; Ascidiacea; Vertébrés; Cordés; Poissons; Ascidiacés. EXTERNAL FORM. 21 iDUs suhstan. ' pass I h roil:; epithelial a- 'ith its inapT • oral opcniii, 1 acci'uiit ()! youii- lamp: iluit the \L velar ti'ii!i\{. iccal cirri ol :. in a hackuv iense-colls. order. (Aliri \.\ of the biicc: cells bupr. lers bear sti: ic same cron;'. 5^,i:.yrJ/I Fig. 7. Velum of Amphioxus seen from (After Lankks- the inside of the pliiirynx. TKR.) Sphincter muscle of velum, Velar tentacles lying across the oral opening. Similar groups of sensory cells occur on the margin of the velum and ii . tentacles (Fig. 7). It may be noted, in anticipation, that the velum is derived directly from the mouth of the larva, which becomes secondarily hid- den from superficial view by the overgrowth of the oral hood. According to Langkr- HANS, similar cells to those mentioned above, carrying stiff sensory hairs, are scattered dif- fusely all over the exter- nal surface of the body. (Cf. Fig. 6 B.) But a concentration of sense- organs comparable to the lateral line of the higher fishes is apparently ; A remarkable structure which seems to combine the properties of gland and sense-organ occurs on the under surface of the oral hood. It consists of a patch of modified epithelium drawn out into finger-shaped epi- thelial tracts, the cells of which carry long cilia. (See Fig. 3.) It was discovered and accurately described by Johannes Miiller, who called it the "Raderorgan" on ac- count of the resemblance of its ciliary movements to those of the wheel-apparatus of a Rotifer. The result of the combined action of the cilia is to cause a flow of water into the pharynx. In connection with the Riiderorgan must be mentioned a special depression forming a peculiar sense-organ (Geschmacksorgan) lying against the right side of the notochord, known as the groove of Please note that t
Size: 1595px × 1566px
Photo credit: © Library Book Collection / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookcentury1800, bookdecade1890, booksubjectfishes, bookyear1894
