1895.] MICROSCOPICAL JOURNAL. 379 



Sponges Considered Microscopically. 



By ARTHUR M. EDWARDS, M. D. 



NEWARK. N. J. 



Sponges, or Porifera may be considered as representing 

 a group by themselves. For a long time they were 

 thought to be vegetables and even nowaday they are so 

 considered by non-scientific persons. But now they are 

 admitted to be animals, though what they are is doubted. 

 We must take the classification of Profs. Nicholson and 

 Lydecker, who give in their Manual of Palaeontology a 

 classification that is eminently satisfactory. Owing to 

 the close likeness of some of the cell-elements of sponges 

 to certain of the Protozoa, tlie entire group has been often 

 referred to that kingdom. Thus some of the cells of a 

 sponge are morphologically identical with the Ama3ba, 

 that formless mass of jelly, while others' present the 

 closest possible resemblance to the flagellated infusoria. 

 Hence a sponge has often been regarded as a kind of 

 colony, the units of which are morphologically Protozoans. 

 Naturalists are, however, now agreed as to the removal 

 of the sponges from the Protozoa ; and they are by many 

 authorities regarded as forming the lowest division of 

 zoophytes (Coelenterata). Other authorities consider 

 that the spoage represents a distinct morphological type, 

 intermediate between the Protozoa and the Coelenterata, 

 and that they are therefore entitled to rank as a separate 

 sub-kingdom, to which the name of Porifera has been 

 given. This is the classification that I have adopted 

 here. 



They may be defined as " multicellular organisms of 

 variable shape, the cells of which are typically disposed 

 to form an outer membrane, an inner membrane, and 

 an intermediate stratum ; and which are traversed by 

 canals which open on the surface, and which are more 

 or less extensively lined by flagellate cells. In most 



