Explanation of the Plates. 



Piate 28. 

 The figures are all drawn after specimens, preserved in spirit, in natural size.) 



Leucoma aspera var. gigantea. 



» » » » Section through ^ jB fig. 1. 



» » » » With numerous appendages. 



» » » ') Section through A £ üg. 2. 



Leucoma aspera var. cramhessa , showing here and there transitions (in 

 shape) to var. gigantea and (in its spicules) to var. typica. 

 Leucoma aspera var. gigantea. Small very flat specimen. 



» » " » Section through A £ üg. i. 



Leucoma aspera. Transition between var. cramhessa and var. gigantea. 



» » Section through A B fig. 5. 



Leucoma aspera var. gigantea. Longitudinal section through the base, 

 showing the entogastric septa. 

 Leucoma aspera var. gigantea. (Other specimen.) 



» » » n Section at right angles through a colony. 



Piate 29. 

 (I used Microscop Hartnack ; Cam. lue. of Zeiss-Oberhäuser.) 



Fig. 1. Leuconia aspera yav. gigantea. Section at right angles to the axis, show- 

 ing the anastomoses of the septa, and the rather thin Sponge-wall. cl.e. 

 = cloacal-cavity. x 4/3. 



Fig. 2. The same. Part of the wall and entogastric septa, which form the pseudo- 

 canals, ps.c. — cl.c. = cloacal-cavity. H. II. Cam. lue. Proj. obj. stage. 



Fig. 3. Leucoma aspera \2kV. Longitudinal section, showing gigantic rods ; one 

 protruding at an angle of about 45°, another totally immerged in the 

 wall. H. IV. Cam. lue. Proj. obj. stage. 



Fig. 4. Reniera cratera 0. S. , showing the structure of the spongin-substance. 

 After a sublimat-preparation. H. VII. Cam. lue. Proj. obj. stage. 



