SPONGIA. 77 



produced ; these have not cilia at first. In the interior of these eggs 

 the contractile cellules have their hirth ; then the spiculse ; and when 

 they are finally covered with the vihratile cilia, aided by them these 

 larvfe of ovoid form swim, or rather glide, through the water. The 

 species of infusoria horn of the sponge resemble the larvae of various 

 polypes at the moment they issue from the egg. " They soon attach 

 themselves to some foreign body," says Mr. Milne Edwards, "and 

 become henceforth immovable; no longer giving signs either of 

 sensibility or of contractibility, while in their enlargement they are 

 completely transformed. The gelatinous substance of their bodies is 

 channeled and riddled with holes the fibrous framework is completed 

 the sponge is formed." 



We may add, however, that other zoologists, and among them 

 MM. Paul Gervais and Yan Beneden, take a different view of the 

 development of the sponges, and Dr. Johnston omits them altogether 

 from his great work on " British Zoophytes." " If they are not the 

 production of polypi," he says, " the zoologist who retains them in his 

 province must contend that they are individually animals, an opinion 

 to which I cannot assent, seeing that they have no animal structure 

 or individual organs, and exhibit not one function usually supposed to 

 be characteristic of the animal kingdom." Gervais and Van Beneden 

 consider, as Milne Edwards does, that the embryos are at 'first 

 movable, then fixed, many of them uniting together, and melting, as 

 it were, into one common colony, which become a sponge, such as we 

 see it. An isolated embryo might also, by throwing out germs, pro- 

 duce a similar colony, which would thus become a product of agamous 

 generation. Thus it appears that Science is far from being settled in 

 its views as to the organization and development of these obscure and 

 complex formations ; nor is it more advanced in its knowledge of the 

 duration of life and the quickness of growth in sponges. It is agreed, 

 however, on one point namely, that the sponge-fisher may return 

 to the same fishing- ground after three years from the last fishing. 

 At the present time sponge-fishing takes' place principally in the 

 Grecian Archipelago and the Syrian littoral. The Greeks and Syrians 

 sell the product of their fishing to the Western nations, and the trade 

 has been immensely extended in recent times, when the sponge has 

 become an almost necessary adjunct of the toilet as well as the stable, 

 and in other cleansing operations. 



