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 



^■"■.'f.'. 



B.Psammoclema 



D. Po^e^ion 



Pig. 84. — External form of various Sponges. A^ Oscaria, an encrusting form, with tlie 

 upper surfac.? raised up into a ntimber of roimded prominences ; iJ, Psaiuiuoclema, a 

 ramifying aubcylindrical Sponge ; C, Euspon^ia (toiler sponge), a massive form with 

 a broad b.ase ; i), Poterion (Neptune's Cup), an cxaiuple of a comple.^ Sponge assuming 

 the form of a vase. (After Vosmaer.) 



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

 {Poterion, Fig. 84, B), 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- 



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