Ill 



PHYLUM AND CLASS PORIFERA 



115 



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- 

 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 



B.Psammoclema 



D.Poherion 



FIG. 34. External form of various Sponges. A, Oscaria. an encrusting form, with the 

 upper surfac.? raised up into a number of rounded prominences; B, Psammoclema, a 

 ramifying subcylindrical 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 Yosmaer.) 



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

 (Poterion, Fig. 84, 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- 

 times the Sponge grows from the narrow base of attachment into 

 a thin flat plate or lamella ; this may become divided up into a 

 number of parts or lobes, which may exhibit a divergent arrange- 



I 2 



