1890-91.] The Structure and Life- History of a Sponge. 437 



Dendy says : " It is probably a general rule in sponges that 

 the ova are fertilised while hanging from the walls of the 

 canal system, and that they migrate first of all through the 

 canal-wall to be fertilised, and then back again into the 

 gelatinous ground-substance to undergo development ; hence 

 the necessity for the amceboid movement so characteristic of 

 sponge ova." 



Before leaving the subject of reproduction in the sponges, 

 it may be interesting to state that besides the natural modes, 

 there is a method of artificial reproduction, somewhat after 

 the manner of plant-cuttings, which has been pursued in the 

 case of the bath sponges, as follows : " The sponge is cut into 

 pieces, about an inch cube, care being taken to preserve as 

 much of the skin and to squeeze out as little of the flesh as 

 possible. The cuttings are then skewered on a strip of cane, 

 and fastened into a wooden frame, constructed to preserve 

 them from the access of mud and excess of light : they are 

 then sunk in the sea at a depth of five to seven yards. In 

 about seven years' time a crop of fine regularly globular 

 sponges is ready for the market." 



I have thus attempted, as stated at the beginning of this 

 paper, to give an outline of a large subject — the structure and 

 life-history of a sponge. Now that I have finished, I am 

 deeply conscious that it is, in reality, but a meagre outline that 

 I have been able to give. Yet it may prove sufficient to 

 incite some one to study more particularly this humble and 

 commonly despised form of animal life, a sponge, with all its 

 busy activities, suggesting the name which Professor Huxley 

 has applied to it of " a subaqueous city." 



Note on "Sea-Fyke." 



A curious use has been made by our jiivenile population of some of the 

 silicious sponges, under the name of " sea-fjke," which deserves passing 

 notice. In the ' Life of James Clerk Maxwell,' by Professors Lewis Camp- 

 bell and "William Garnett, two schoolboy letters of the great scientist are 

 given, in which reference is made to this mysterious substance. One of 

 these letters contains the following passage : " There was a boy that 

 brought sea-fyke to the school, and put it down the boys' backs, for which 

 he was condemned to learn 12 lines for 3 days." The school referred 

 to is Edinburgh Academj- ; and in a footnote the learned authors describe 

 the substance as " often found on the sea-shore." They go on to say : " It is 



