374 BULLETIN OF THE UNITED STATES FISH C0MMI8SI0N. 



REPLY BY MR. R. M. BACHE. 



I agree entirely with the opiuion that the practice of coating surfaces, 

 unless the coating could be very cheaply executed, would not be profit- 

 able in this country. Obviously, the difference between this country 

 and other countries generally, in this respect, is the same as that which 

 in this country precludes the close culture obtainiug in Europe and 

 elsewhere in the cultivation of land. But that admitted, it still re- 

 mains the fact, which Mr. Ryder concedes, that if some surface could 

 be found or cheaply manufactured from which spat could easily be de- 

 tached, a great desideratum would be supi)lied. I have been much 

 impressed with this throughout my observation of this shore. 



I do not find that the spat has any substance or surface of predilec- 

 tion. I find it uniformly distributed on twigs, bark, tin, shells, bricks, 

 stones, &c. On all these it is closely adherent; so much so as to be in- 

 separable without mechanical force sufficient to break the shells of the 

 smaller animals. Thus the embryo, having run the gauntlet of cur- 

 rents, predatory animals, mud, sand, &c., and having reached a certain 

 point of development, which would seem to secure a fair chance of ex- 

 istence to maturity, is really still engaged in as severe a struggle for 

 •existence as at first, for germ crowds upon germ, so as often to make 

 an incrustation of two or three layers from the same season's spawning. 

 This is inevitable; but, in considering the question from a commercial 

 point of view, what does not seem to be inevitable is that such multi- 

 tudes of spat should be destroyed in the attempt to procure seed. The 

 destruction is as nothing compared with that from nature's action, but 

 these animals of which I am speaking are in the merchant's hands to be 

 utilized, and in utilizing them he destroys m;vriads. 'Putting out of the 

 question the mere loss of individuals, this represents lost labor. 



It is, then, most imx)ortaut that spat caught should be available, and 

 I see in none of the surfaces adopted one which combines efficiency and 

 cheapness. The question of the shape of the surface seems uot to have 

 attracted much attention, but it is an important factor in the problem. 

 However, that apart, for we are concerned at present more particularly 

 with detachability as derived from character of surface as distinct from 

 its form, and although its character (as in the roughness of stones) is 

 directly related to indetachability, I confine myself to fragility of sur- 

 face. If, then, there can be no objection to pitch (see page 33, part 2, 

 of the "Practical Guide," &c., by Felix Fraiche) on account of its 

 aromatic principle, I should suppose that it would be what is required 

 to produce fragility of surface combined with economy of preparation. 

 At ordinary temperatures pitch makes a very brittle film, and at mod- 

 erate temperatures it softens under water ; even in the summer it would 

 be brittle ; in the sun it would be sottish. Put on it the highest temper- 

 ature convenient, so as to have the slightest film, dipped or brushed, it 



