158 BRITISH SPONGES: 



insect which Mr Westwood has denominated the Branchiosto- 

 ma Spongillae,*) or crustacean or molluscan. Nearly every spe- 

 cimen of Spongilla is indeed a rich nestling place for one or moi'e 

 species of these classes, but thence to conclude that it is by 

 means of their respiration that the currents which enter into and 

 flow out from the pores and oscules of the sponge are generated 

 and kept alive, is at variance with the previous observations of 

 Grantf and Dutrochet. Nor does the cause assigned seem ade- 

 quate to the explanation of the phenomena, which are very dif- 

 ferent from those presented by the intennitting currents occa- 

 sioned by the breathing of any animal I have observed ; and it 

 is difiicult to believe that a current which is uniform and conti- 

 nuous, and always directed in one course, can depend on any 

 cause which, like the action of breathing, must vary every mo- 

 ment in intensity, quickness, and in position, by the motions and 

 actions of the animals. 



The structure of the fresh-water sponges is so like that of the 

 Halichondrise, that Dr Fleming has deemed their separation un- 

 necessary, but the systematists who have done otherwise are 

 justified in their views by the looser texture of the Spongilla, its 

 green colour, the existence of the seminiferous capsules at sea- 

 sons in the cells, and the peculiarity of its habitat. Oken ap- 

 pears first of all to have proposed this separation, but the name 

 which he conferred on the genus, as well as that subsequently 

 given to it by Lamouroux, has yielded to the superior influence 



* For notices of this animal see Athenaeum for 1838, p. 899 ; Charles- 

 worth's Mag. Nat. Hist. iii. p. 200 ; Ann. and Mag. Nat. Hist. vi. p. 

 315 ; Lin. Trans, xviii. p. 390. 



t " The whole arrangement of the spicula, around the canals, shows 

 that these are not accidental passages, formed by worms or aquatic in- 

 sects in a vegetable substance, and helps to prove that its currents are 

 not produced by any foreign intruders, though this substance is infested 

 with myriads of ciliated animalcules, which are constantly producing cur- 

 rents to attack their prey." — Grant, 



