ACALEPH^. 101 



whilst the pharynx, or first division, is disproportionately enlarged 

 and, being highly vascular, and beset with vibratile cilia, performs 

 the chief part of the respiratory function. 



But before proceeding to the great primary group of hetero- 

 gangliate animals, to which we are thus conducted, it will be 

 necessary first to consider the larger forms of Radiata, which seem 

 to diverge from the Anthozoic division of the Polypi of Cuvier. 



LECTURE IX. 



ACALEPH^. 



CuviER, after having allocated a certain proportion of the Vermes of 

 Linnaeus in his two great primary groups, Mollusca and Articulata, 

 left the remainder to form a fourth sub-kingdom of animals under 

 the name of Radiata^ of which we have now to consider the highest 

 organised species. 



It is true that the animals which last occupied our attention have 

 a radiated arrangement of the prehensile organs about the mouth ; 

 but the only classes containing species with a radiated form of the 

 entire body, are those to which the term Radiaria has been applied 

 by Lamarck. These are animals of more complicated organisation 

 than the Anthozoic polypes, the large, soft, gelatinous species of 

 which lead to the still larger, softer, and more gelatinous forms of the 

 present class. 



The true radiated Invertebrata have been divided into two groups, 

 according to the nature of their integuments, which, in the one, is 

 soft and gelatinous, in the other coriaceous, or calcareous, and ge- 

 nerally armed with spines. The species of both classes are aquatic 

 and marine, and both are extensively diffused through all the climates 

 of the globe. The soft-bodied Radiaria float in the free and open 

 sea : to the shores and fathomable depths are limited the better 

 defended groups, as being better able to bear the brunt of the cease- 

 less conflict between land and water. 



The gelatinous oceanic Radiaries are remarkable for the singularity 

 and beauty of their forms and colours : they give variety and animation 

 to the otherwise monotonous waste of waters which are most remote 

 from land. They there surprise and delight the weary navigator by 

 their mimic fleets, glistening with all the brilliant hues of the rain- 

 bow. They tantalise the naturalist-collector both by their bright 



H 3 



