THE PORIFETIA. 81 



water sponge found in very deep pools in a South American 

 river, more than two hundred miles from the sea (river 

 Uruguay),* together with some others of like form from deep 

 parts of an inland lake (Lake Baikal), t Dr. Bowerbank 

 described this Uruguay species in his " Monograph of the 

 Spongillidae " (Proc. ZooL Soc, Nov., 24, 1863), under the 

 name Sponr/iUa coralloides, but Mr. Carter (Annals and 

 Mag, Nat. Hist., Feby. 1881), created a new genus for it, 

 Uriiguaya, and grouped it with the other sponges of similar 

 growth just alluded to, Luhomirskia baicalensis, and its 

 varieties. 



Isodictya varia^is, until the discovery of the sponge in 

 the Mersey, was only known by ''a small fragment surround- 

 ing two adjoining branches of a small Fuciis, forming two 

 parallel and united cylinders of sponge, an inch in length, 

 and seven lines in width, and varying in thickness from 

 one to two lines, sent to Dr. Johnston by Mr. Barlee, 

 from Shetland." Whether this fragment was brought up 

 by the dredge or was picked up on the shore does not 

 appear. It is, however, clear that it is not common on our 

 coasts as a marine species, whilst the great profusion in 

 which it was found at Egremont under the circumstances 

 already stated (for the bed of the stream was thickly covered 

 with it), indicates that the conditions of life there were most 

 favourable for its growth and development. It thus appears 

 to form a link between marine and fresh water sponges. 

 Marine sponges reproduce by means of ova and spermatozoa, 

 and fresh water sponges can also reproduce in this way, as was 

 shown by Lieberkiihn in 1856 {Beitrdge zur Entwickelungsge- 

 chichte der Spongillen, Archiv /. Anat. u. Physiologie, Heft 

 i, u. ii, pp. 1-19, January), but all fresh water sponges, with 



* Proc. Lit. and Fhil. Soc. Liverpool^ 1877-8, vol. 32, p. Ivi— *' On a 

 fresh-water Sponge from Babia," T. Higgin, F.L.S. 



\ Annals and Mag. Nat. Hist., Feby., 1881, and July, 1884. 



F 



