1889.] on the Llfe-ld story of a Marine Food-nsTi. 387 



their eggs on the bottom. In the same way the very small eggs of 

 the flab proYide for a large annual increase of the species. 



The translucent eggs, which, unless they contain a globule 

 of oil, as in Fig. 1, are difficult to see in some instances even 

 in a glass vessel, thus escape (by floating throughout the water) the 

 vicissitudes to which a purely surface-life would expose them, such 

 as the admixture of the surface-water with rain, and the attacks of 

 gulls, ducks, and other forms ; and they also are less at the mercy of 

 the active predatory races living on the bottom, not to allude to the 

 risks of being swept by storms on the beach or captured and de- 

 stroyed by the ground-rope of the trawler. Nature indeed could have 

 devised no method more secure than this for the safe increase of 

 those valuable fishes which for ages have peopled our waters, and, 

 with Prof. Huxley, I venture to say, will perhaps people them for 

 ages yet to come, notwithstanding the persistent efforts of man to 

 annihilate them. 



Some good observers, for example, Prof. Piyder in America, have 

 attached much importance to the oil-globule in eggs which are 

 pelagic ; but its buoyant influence has been slightly over-estimated, 

 for, as he himself shows, some contain no oil-globule, while the 

 massive oil-globnles in the eggs of the salmon and cat-fish have no 

 such eflect.* They float, as well shown by lEi*. Edward E. Prince,! 

 solely in virtue of their specific gravity, which is somewhat less than 

 that of sea-water. The moment fresh water is added they sink, as 

 they likewise often do when transferred from a vessel filled at sea 

 into one containing shore- water. 



AYhile immediately after deposition these minute spheres are 

 prone to accident from impurity and sudden changes in the tempera- 

 ture of the water, such would not seem to be the case after develop- 

 ment has made some progress. Thus many living eggs will be 

 found in odoriferous vessels brought from sea by the fishermen if the 

 enclosed embrycs have re^iched an advanced stage. Again, while 

 carrying out some experiments on temperature (at the suggestion of 

 Prof. Huxley^ during the Trawling Expeditions, I had occasion to 

 heat a test-tube containing some of the eggs of the flounder, so as to 

 make them rush up and down the vessel most actively. Considerable 

 heat was applied, and under the impression the eggs were irretrievably 



* Prof. Eyder classifies buoyaut ova into (1) those in wliicli the specific 

 gravity of the yolk is diniinislied, ex. cod ; (2) those in which large oil-drops in 

 an eccentric position aid in causing the eggs to float ; and (3) those in which a 

 very large oil-drop caused the ovum to float even in fresh water. Mr. Prince 

 has shown that tl,e number of buoyant eggs without oil is at least equal to the 

 number with oil-drops. The statement of the former, therefore, that the cod's 

 egg is unique in floating by the diminished specific gravity of the protoplasmic 

 matter of the vitellus does not traverse the view of the latter. Moreover, it mnst 

 be remembered that the oil-globnle in many is not permanently eccentric, but 

 moves throughout the yolk. 



t Secretary to the Mussel and Bait Committee. 



