18 THE BRITISH SPONGES. 



nic mucus that fills the intercellular spaces. I have never 

 met with similar capsules in any marine sponge. * In the 

 Tethya, and in one or two Halichondrise, there are occa- 

 sionally found oviform bodies, lying apparently loose in the 

 Tethya, but so firmly attached to the fibres of the Hali- 

 chondrise, that they are not easily detached : they are large 

 enough to be visible with the naked eye, are of a roundish 

 or egg shape, and are composed of a gelatinous basis, in 

 which numerous spicula are immersed. Indeed, in struc- 

 ture they do not differ essentially fi'om the parent, and 

 seem to be young or embryo sponges developing them- 

 selves within the body, whence probably they escape when 

 this has died and decayed. They can scarcely be consi- 

 dered identical with the ova which Dr Grant discovered 

 that a few sponges produced in the spring season, for he 

 describes these as being more regularly egg-shaped, of a 

 yellow or orange colour, and covered with vibratile cilia, ex- 

 cepting on the narrow end, which is naked of them. These 

 ova in fact resemble very exactly the reproductive gem- 

 mules of the ascidian polypes ; and, when matiu'e, being de- 

 tached and carried from the parent mass by the effluent 

 currents and the movements of their own cilia, they float 

 and swim about in the sea until they have found a place 

 suitable for their growth and developement. But in 

 truth these ciliated ova and the oviform bodies are 

 found in so very few species, and so seldom even in 



" Ehrenberg it seems has seen them " in very many sponges of the 

 Red Sea." Hogg in Lin. Trans- xviii. p. 40]. Mr Hogg has endeavour- 

 ed to show that long before Donati liad represented similar cajisules in a 

 Tethya in his Stor. Nat. dell' Adriatico, tab. viii. fig. C, c, i, and fig. E, 

 a, a ; and Muller in another sponge, evidently referable to the same ge- 

 nus, (Zool. Dan. tab. 157, fig. 1, 2, a,b.); but these bodies, vrhich I 

 have also seen, are not s^iniilar to the capsules of Spongilla. 



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