14 MALACOZOA. 



The vast series of animals destitute of a brain and 

 spinal cord, protected by a skull and vertebrae, has, by 

 Cuvier and many other Zoologists, been considered as 

 naturally divisible into three distinct portions, forming, 

 as it were, three diiferent tj-pes of organization. To these 

 three groups have been given the names of JMollusca, 

 Articflata, and Radiata, or Soft Animals, Jointed Ani- 

 mals, and Rayed Animals. The Greek terms ]\Ialacozoa, 

 ExTOMozoA, and Actinozoa, also employed to designate 

 these groups, are more appropriate. 



The IMalacozoa, although some of them approach 

 more nearly in structure to the Osteozoa or Yertebrata, 

 are, as a whole, inferior in their organization and 

 faculties to the Entomozoa, but superior to the Actino- 

 zoa, and may therefore be -sdewed as forming the thii'd 

 type or series of the animal kingdom. 



Considered with respect to their external form, the 

 Malacozoa vary exti^emely, insomuch that no general 

 idea can be given of it. Their internal parts are always 

 soft, although, in a small number of them, there are 

 some solid internal pieces intended for the protection of 

 certain organs. Their nervous system is composed of 

 ganglia and nerves . The principal mass of these ganglia, 

 which may in some respects be compared to the brain, 

 forms a kind of collar round the oesophagus, and other 

 ganglia are dispersed throngh the body, but not in sym- 

 metrical order, nor forming a chain, as in the Entomozoa. 

 A few species have organs analogous to the ear ; many 

 are furnished with eyes ; but it is not certain that any 

 have a particular organ for smell ; and it appears that, in 

 very many of them, there are no other organs of sense 

 than those subservient to touch and taste. The oro;ans 



