156 THE MICROSCOPE AND ITS REVELATIONS. 



first radials (r 1 ); whilst the anal plate (a) is now lifted nearly to the 

 level of the second radials (r 2 ), by the development of the anal funnel 

 or vent (v) to which it is attached. The oral plates are not at first appa- 

 rent, as they no longer occupy their first position; but on being carefully 

 looked-for, they are found still to form a circlet around the mouth (fig. 

 3, 0, 0), not having undergone any increase in size, whilst the visceral disk 

 and the calyx in which it is lodged have greatly extended. These oral 

 plates finally disappear by absorption; while the fiasals are at first con- 

 cealed by the great enlargement of the centro-dorsal (which finally ex- 

 tends so far as to conceal the first radials also); and at last undergo 

 metamorphosis into a beautiful 'rosette/ which lies between the cavity 

 of the centro-dorsal and that of the calyx. In. common with other mem- 

 bers of its Class, the Antedon is represented in its earliest phase of develop- 

 ment by a free-swimming ' larval zooid' or pseudembryo, which was first 

 observed by Busch, and has been since carefully studied by Pro. Wyville 

 Thomson ! and Goette . 2 This zooid has an elongated egg-like form, and 

 is furnished with transverse bands of cilia, and with a mouth and anus of 

 its own. After a time, however, rudiments of the calcareous plates form- 

 ing the stem and calyx begin to show themselves in its interior; a disk 

 is then formed at the posterior extremity, by which it attaches itself to a 

 Sea- weed (very commonly Laminaria), Zoophyte, or Polyzoary; the calyx, 

 containing the true stomach, with its central mouth surrounded by ten- 

 tacles, is gradually evolved; and the sarcodic substance of the pseudem- 

 bryo, by which this calyx and the rudimentary stem were originally in- 

 vested, gradually shrinks, until the young Pentacrinoid presents itself in 

 its charateristic form and proportions. 3 



1 ' On the Development of Antedon rosaceus ' in " Philos. Transact." for 1865, 

 p. 513. 



2 "Archiv f. Mikrosk. Anat.," Bd. xii., p. 583. 



3 The general results of the Author's own later studies of this most interesting 

 type (the key to the life-history of the entire Geological succession^ of Crinoidea) 

 are embodied in a notice communicated to the 

 for 1876, p. 211, and in a sul 

 cently made to our knowled^ 



der Crinoideen' (Leipzig, 1877), forming part of his " Morphologische Studien an 

 Echinoderinen," is the most important. 



