TIT 



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 1 tranches 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 



Fio.84 — External form of various Sponges. A, Oscaria, an encrusting form, with the 

 upper surfac.-.- raised up into a number of rounded prominences; B, Psarumoclema. a 

 ramifying subcylindrical Sponge ; C, Euspongria (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.) 



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- 



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