INTBODUCTION. 3 



partly on account of the unattractive appearance of 

 many of the species, but more so because of the im- 

 possibility of making them into pleasing objects for 

 the cabinet, as all colour leaves them when they are 

 placed in spirit. It would be erroneous, however, to 

 suppose that they are devoid of beauty, for many of 

 them must rank among the most charming objects 

 met with in our rock-pools, and some species from the 

 deeper waters rival, in the intensity and purity of 

 their colours, the rich hues of fruits and flowers. 

 Many are splendidly hyaline, others, again, are just 

 transparent enough to reveal the mellow tints of their 

 viscera, producing a rich, lucid appearance. But the 

 most attractive of all are perhaps the stellate Botrt/lli, 

 which spread over stones and fuci in large gelatinous 

 patches of brilliant green, orange, red, and yellow, the 

 colours being intensified in the individuals which are 

 immersed in, and studded over, their investing test in 

 radiating systems. 



They are all possessed of the highest interest to 

 the philosophical inquirer on account of their physio- 

 logical and anatomical peculiarities, as well as for the 

 light which they throw on the structure of their 

 zoological relatives, leading as they do to a fuller com- 

 prehension of the organisation of the Lamellibranchiata 

 on the one side, and of the Bryozoa and the Brachio- 

 poda on the other. 



The Tuuicata are the Tctlnjum of Aristotle.* They 

 were well known to the Father of Natural History, who 

 appears to have justly appreciated their true nature, 

 for he recognised their relationship to the ordinary 

 bivalve Mollusca, and was aware that the test was the 

 homologue of the shell of the higher mollusk. 



After his time scarcely anything f is heard of these 

 animals until about the middle of the 16th century, 



* ['Historia Aninmlium/ lib. iv, cap. 6; and ' De Part. Anim.,' lib. iv, 

 cap. 5. (Cir. B.C. 330.) ] 



t " Nothing " in the authors' MS., biit see Pliny, ' Hist. Anim./ lib. xxxii, 

 cap. 30, 31, and Julian, ' De Nat. Anim.' 



