O A MONOGRAPH OF THE AUSTRALIAN SPONGES, 



other Sponges. The Mesoderm between them is filled with bipolar 

 and multipolar tissue cells and also contains a few wandering 

 amoeboids (fig. 4). 



The thick threads pervading the gastral cavity are covered by a 

 flat Epithelium, which is not different from the ectodermal Epithe- 

 lium of the outer surface and inhalent canal system. The most 

 prominent elements in this ])art of the Sponge are the sexual 

 products, which at certain seasons take up nearly the entire 

 substance of these gastral threads. 



The amceboid wandering cells. 



Partly by observations on the distribution of these elements 

 and partly by a series of experiments, I have been led (1) to 

 assume that they absorbed digestible matter, which is transmitted 

 to them by the Epithel cells on the upper side of the Subdermal 

 cavities in certain Aplysinidte. 



The distribution of these elements in our Sponge also points to 

 a similar function. They are most numerous just below the inner 

 siii-face of the skin, and met with, less abundantly, also in other 

 parts of the Sponge. 



I had no opportunity of observing these cells in the live tissue, 

 but the images represented by good sublimate and Alcohol speci- 

 mens on sections are exactly like those described by me (I.e.) 

 in the case of Aplysinidte. 



The Gland Cells. 



These elements have the same position as the corresponding 

 elements in Aplysinidse (2), and are also of similar shape. They 

 appear pear-shaped and attached to the outer surface by two to 

 four slender threads. They measure 0*01 x 0-002 mm. 



(l)E.v. Lendenfeld. Neue Aplysinidaj. Zeitschrift fiir wissenschaftliche 

 Zoologie. Band XXXVIII., Seite 249, ff. 

 (2) R. V. Lendenfeld. L.c. Seite 254. 



