TUNICARIES. 221 



energy as upon the earth's surface, and in its 

 atmosphere, so formed them as to suit the cir- 

 cumstances in which they were to be placed, 

 Instead of sending the social aquatic animals 

 forth by myriads to collect food and materials 

 for their several buildings, he took the vegetable 

 creation for the type of their general structure, 

 in many cases fixed them to the rock or stone, 

 united them all into one body, which, under a 

 common envelope, contained often innumerable 

 cells from which were sent forth by the occupant 

 of each a circle of organs to collect food, from 

 which, by some chemical operation, they could 

 elaborate materials for the enlargement of their 

 common house ; and often cause that influx and 

 reflux, to compare small things with great, 

 resembling the oceanic tides, and by which the 

 sea-water is alternately absorbed and rejected by 

 these animals : but this function, in the case of 

 some of the Tunicaries, the animals with which 

 we are now concerned, seems to be affected by 

 a central organ or pump common to the whole 

 fraternity. 



But although none of the marine associated 

 animals are employed, like the terrestrial ones, in 

 labours that require locomotion and the collec- 

 tion, from different and often distant parts, of 

 materials for the erection of their several fabrics, 

 and of food to store up for the maintenance of 

 the various members of their community, yet 



