. The Cambridge natural history. Zoology. 6o6 ECHINODERMATA out into short tag-like processes, in which we may distinguish (following Mortensen's '^ notation) in the prae-oral loop an anterior median process (Pig. 283, ), and a pair of prae-oral pro- cesses (). In the post-oral loop there is a median dorsal process () and paired anterior dorsal (), posterior dorsal (), posterior lateral (), and post-oral () processes. At the apex of the prae-oral lobe between prae-oral and post- ural ciliated rings there is an ectodermic thickening, recalling the so-call
. The Cambridge natural history. Zoology. 6o6 ECHINODERMATA out into short tag-like processes, in which we may distinguish (following Mortensen's '^ notation) in the prae-oral loop an anterior median process (Pig. 283, ), and a pair of prae-oral pro- cesses (). In the post-oral loop there is a median dorsal process () and paired anterior dorsal (), posterior dorsal (), posterior lateral (), and post-oral () processes. At the apex of the prae-oral lobe between prae-oral and post- ural ciliated rings there is an ectodermic thickening, recalling the so-called apical plate of Annelid larvae. (2) The OpMopluteus, the larva of the Ophiuroidea. In arm. Fia. 284. âA, Ophiopluteus of Ophiothrix fragilis. Hydrocoel; , left posterior coelom ; oes, oesophagus; , right posterior coelom; st, stomach. B, metamorphosis of Ophiopluteus of Ophiura sp. (After Johannes Miiller.) this type the prae-oral lobe remains small, and the primitive â ciliated band is undivided. The processes into which it is drawn out are very long, and are supported by calcareous rods. Of these processes we may distinguish prae-oral, postero-dorsal, postero-lateral, and post-oral. The postero-lateral are always much longer than the rest, so that the larva when swimming appears to the naked eye as a tiny V. In the case of Ophiothrix fragilis (Fig. 284, A) the postero-lateral processes are many times longer than the rest of the body. The Ophiopluteus was the first Echinoderm larva to be recognised. It was discovered by Johannes Miiller,^ who also discovered the other three types of ' "Die Echinodermenlarven der Plankton Expedition," Ergebn. Plankton Exp. Bd. ii. J, 1898. - " tiber die Larvenzustande und die Metamorpliose der Ophiuren und Seeigel," Abh. K. Akad. loiss. Berlin, 1846, and other papers in the same publication in sub- sequent Please note that these images are extracted from scanned page image
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Keywords: ., bookcentury1800, bookdecade1890, booksubjectzoology, bookyear1895
