438 GENERAL CHARACTERS OF RADIATA. 



This is the Sponge tribe, which has been united by Blainville 

 with some others into a group, which he terms Amorphozoa^ or 

 form-less animals. It is through these curious beings, that the 

 connection between the Animal and Vegetable Kingdoms is most 

 completely established. These Kingdoms approach each other, 

 not through the most perfect forms of either, but by the most 

 simply- organised members of each. Among the lowest Plants, 

 the greatest indefiniteness of form prevails ; and we are prepared 

 to expect, therefore, a similar indefiniteness in the lowest groups 

 of Animals. This obviously results, in both cases, from the low 

 degree in which distinct or special organs are developed. In 

 proportion as each minute division of the structure performs all 

 the functions essential to its life, it will be independent of the 

 rest ; and the whole structure will thus approach the condition 

 of an inorganic mass, in which each particle exists by and for 

 itself, and of which the form is entirely determined by circum- 

 stances external to it. The Sponges have a much closer connec- 

 tion with the group of Radiata, than they have with any other 

 division of the Animal Kingdom ; for one of the divisions of the 

 Polypifera may almost be regarded as consisting of Sponges 

 advanced to a higher grade of organisation. We may, then, 

 place them on the border of this group ; in sueh a position as to 

 stand at that extreme edge, as it were, of the whole Animal 

 Kingdom, which approximates the Vegetable Creation. 



991. There are certain other forms of this group which, on a 

 cursory view, would seem as little characterised by the Radiated 

 structure as the Sponges themselves. When we look at a mass 

 of branching Coral of any description (Fig. 623), we at once 

 perceive its resemblance in form to the productions of the Vege- 

 table Kingdom, and we are at a loss to detect any regular arrange- 

 ment of its parts, still less that circular symmetry for which 

 we are seeking. But we must remember that this structure is 

 merely the frame-work, which connects a number of individuals 

 capable of existing separately ; and it is in these, that we must 

 seek for the radiated conformation. This we find very distinct 

 in the Polypes themselves ; and, in one group, it is marked in 

 the stony cells which they form (Fig. 619). 



992. If we ascend from the lowest to the highest RADIATA, 



