THE ANNALS 



AND 



MAGAZINE OF NATURAL HISTORY. 



[SECOND SERIES.] 



•* _.. perlitora spargitc museum. 



Naiades, et circClm vitreos considitc foutes : ^ 



PoUice virgineo teueros hic carpite flores : 

 Floribus et pictum, liivse, replete canistnim. 

 At vos, o Nympha Craterides, ite sub undas j 

 Ite, recuryato variata corallia trunco 

 Vellite muscosis e rupibus, et mihi conchas 

 Ferte, lies pelagi, et pingui conchvlia succo." 



S.'PaTtkenii GiaHHettaiii Eel. I. 



No. 73. JANUARY 1854. 



I. — On the Structure of the Echinoderms. 

 By Johannes Mlller=»'. 



[With a Plate.] 



IN addition to tlieir radial form aud division, the Ecliinoderma 

 are essentially characterized by the calcification of their perisoma 

 and of many internal parts, by their peculiar metamorphoses, 

 and especially by their ambulacral organs, feet or suckers, which 

 may be distended by means of a peculiar system of internally 

 ciliated canals. 



The larvEe of the Echinoderms are bilaterally symmetrical, 

 and present no trace of a radial arrangement ; when impelled by 

 their cilia, it is always one end which is directed fonvards. The 

 radial an-angement is met with only in the adidt Echinoderm 

 forms, and even they always present more or less obvious traces 

 of a bilateral symmetry. In those Holothurm which creep upon 

 an ' ambulatory region ' (Sohle) and in the irregular Eckinida, 

 the bilaterality is at once obvious. But all Echinoderms do not 

 constantly creep on the same surface, or in other words, possess 



* Read before the Royal Academy of Sciences of Berlin, May 26, 1853. 

 Translated and communicated by Thomas Huxley, F.R.S. 

 Ann. ^- Mag. N. Hist. Ser. 2. Vol. xiii. 1 



