116 



ZOOLOGY 



SECT. 



branched (Fig. 85, B). Sometimes vertical and horizontal growth 

 is almost equal, so that eventually there is formed a thick, solid 

 mass of a rounded or polyhedral shape (Fig. 85, C), with an even, 

 or lobed, or ridged surface. Very often, after active vertical growth 

 has resulted in the formation of a comparatively narrow basal 

 part or stalk, the Sponge expands distally, growing out into lobes 

 or branches of a variety of different forms, and frequently anasto- 





C,E usbongia 



B.Psammoclema 



. Poferion 



FIG. 85. External form of various Sponges. A, Oscaria, an encrusting form, with the 

 upper surface raised up into a number of rounded prominences ; B, Psammoclema , a 

 ramifying subcyliiulrical Sponge ; C, Euspongia (toilet sponge), a massive form with 

 a broad base ; D, Poterion (Neptune's Cup), an example of a complex Sponge assuming 

 the form of a vase. (After Vosmaer.) 



mosing. Sometimes, after the formation of the stalk with root- 

 like processes for attachment, the Sponge grows upwards in such 

 a way as to form a cup or tube with a terminal opening. Such a 

 cup-shaped Sponge, exemplified in the gigantic Neptune's Cup 

 (Polerion, Fig. 85, D), is not to be confounded with the simple 

 vase or cup referred to above as the simplest type of Sponge, 

 being a much more complex structure with many oscula. Some- 



