TRICHOPLAX, THE DIGYEMIDjSS AND OUTHONBGTWjE. 63 



CHAPTER IV. 



rKICHOPLAX, THE DICYEMID^ AND ORTHONEOTIDtE. 



Befoee passing on to a description of the first type of 

 Metazoa, it will be necessary to consider a few forms which 

 can hardly be assigned to it and yet present too great a dif- 

 ferentiation of their component cells to warrant their reference 

 to the Protozoa. A third subkingdom, the Mesozou, has been 

 proposed for them, but until more is known of the relations 

 of some of them at least to other forms the establishment of 

 such a subkingdom seems inadvisable. 



Trichoplax adhcerens. 



Pig. 30.— .4, Sukface View akd B Transvekse Section through Tricho- 



plax (after Schhlze). 



b = bolryoidal structure. r = lefiactive bodies. 



In the marine aquaria at Gratz, Vienna, and Berlin there 

 has been found a small organism (Fig, 30, A) measuring from 



