OP THE SPONGIAD^. 91 



classes of animals, we must bear in mind that the term 

 sarcode is applied in the sense in which it is employed by 

 Kolliker in his observations on Actinophrys Sol, and in 

 accordance with its appearance and functions in the Amoebae, 

 and not in the more extended sense and general application 

 of the word as applied to muscular masses of flesh. 

 Dujardin has also employed the same term in the same 

 sense many years before Kolliker wrote on these subjects. 



As we descend in the organic scale of life, we find the 

 great systems of animal functions, the osseous, the muscular, 

 the nervous, the sanguineous, all becoming simplified, until 

 at last one or more of them is found entirely wanting. 

 But the sarcodous digestive system appears never to be 

 absent. We find it from the highest organized mammals 

 in the form of the mucous lining of the alimentary organs, 

 passing through animals of every degree of development, 

 until the animal itself becomes simplified to the degree of 

 appearing as a mass of gelatinoid sarcode only, or with 

 possibly a central nucleus of membrane, as in Actinophrys 

 Sol, &c. 



The presence of the stomach has been insisted upon by 

 some naturalists as the organ absolutely necessary to con- 

 stitute an animal. On the contrary, it would appear, from 

 its functions in the higher animals, that it is at best but a 

 preparatory organ for the less striking but more important 

 one of the sarcodous system which appears invariably to 

 cover, the digestive surfaces of animals. In mammals it 

 has hitherto been considered by many physiologists as a 

 subordinate portion of the digestive system, a merely 

 lubricating material to assist the passage of the fecal 

 matters in its course downwards. On the contrary, if we 

 view it in the light in which it exhibits itself as sarcode, 

 and not as mere mucous effusion, it becomes the ultimate 

 and most important part of the digestive system ; the final 

 receptacle, through its wonderful inherent powers of imbi- 

 bition of the fully elaborated pabulum presented to it, and 

 the ultimate refiner and digester of all the nutriment that is 

 destined to pass into the sanguineous system. 



If we examine the digestive surface of the sacular polypi, 



