EXPLANATION OF PLATE XVI. 



FIG. ^ 



1-3. RHIPIDODENDRON SPLENDIDUM, St. (Stein). Flabellifbrm compound colony- 

 stock or zoothecium, consisting of several hundred closely-united tubules, 

 the entire structure representing the product by repeated subdivision and 

 excretion of a primarily single monadiform animalcule, x 400 ; 2, young 

 zoothecium, constructed up to the point of bifurcation by a single monad, 

 which then dividing by longitudinal fission, has produced two parallel tubes 

 x 600 ; 3, an isolated monad, x 1150. 



4-8. RHIPIDODENDR^N HUXLEYI, S. K. 4, Detached ramiscule from an adult 

 branching zoothecium, x 170; 5, portion of branchlet, showing quadruple 

 tubular construction, x 300 ; 6, distal termination still more magnified, 

 showing contained monads, x 800 ; 7, diagrammatic illustration of mode in 

 which the characteristic branching zoothecium is produced, the four primary 

 monads, as at a, dividing by longitudinal fission, the right and left halves of 

 such total product then parting, as at b, and forming their respective tubules 

 at divergent angles ; 8, symmetrically developed adult zoothecium, x 5 ; 

 9, an adult zoothecium, natural size. 



