SPONGES. 391 



stances Lieberkiihn found that the globular arrangement 

 no longer existed, the globules being replaced by granules 

 exhibiting an active molecular motion. That the gem- 

 mules are formed from agglomerations of sponge-cells may 

 be readily proved in the branched sponge containing 

 smooth gemmules. Lieberkiihn notices four kinds of 

 gemmules characterised respectively by their cases or 

 shells. 



1. Those with smooth cases. 



2. Those "with stellate amphidiscs. 



3. Those with amphidiscs, in which the discoid ex- 

 tremities are entire, and not stellate. 



4. Gemmules whose case, instead of amphidiscs, is fur- 

 nished with minute, usually slightly curved siliceous 

 spicules. 



It would appear, therefore, that the " globules " of 

 Meyen are nothing more than altered sponge-cells. The 

 autumn is the most favourable season for observing the 

 process of their formation. 



In the journal of the Bombay branch of the Eoyal 

 Asiatic Society for 1849, Surgeon H. J. Carter gives a very 

 accurate account of fresh-water sponges found in the 

 water tanks of Bombay. Of five species that he disco- 

 vered, one was the Spongilla friabilis, the others he named 

 Sp. cinerea, Sp. alba, Sp. Meyeni, Sp. plumosa. 



Spongilla cinerea is stated to present on its surface a 

 dark rusty, copper colour, lighter towards the interior, and 

 purplish under water. It throws up no processes, but 

 extends horizontally in circular patches, over surfaces two 

 or three feet in circumference, or accumulates on small 

 objects ; and is seldom more than half an inch in thick- 

 ness. It is found on the sides of fresh-water tanks, on 

 rocks, stones, or gravel. The ova are spheroidal, about 

 l-63d of an inch in diameter, presenting rough points ex- 

 ternally. Spicula of two kinds, large and small ; large 

 spicula, slightly curved, smooth, pointed at both ends, 

 about l-67th of an inch in length ; small spicula, slightly 

 curved, thickly spiniferous, about l-380th of an inch in 

 length. 



Spongilla friabilis. — Growing in circumscribed masses, 

 on lixed bodies, or enveloping floating objects ; seldom 



