THE PELAGIC STAGES OF VolXG FISHES. 3 



egga in which there are no large globules, no concentration of the fatty 

 masses, as in Ctenolabius and the like (Pis. VII., VIII, IX. ), and those in 

 which we find one or two globules. The fact that in the Cottoids we see 

 the gradual concentration of these fatty masses to a smaller number of large 

 globules as the egg advances in age, and furthermore the coalescence of two 

 globules into one, would lead us to consider as of little importance this dis- 

 tinction of eggs based upon the presence or absence of globules. The oil- 

 globule is often retained in quite advanced embryos. 



We next find pelagic eggs which are laid singly, — that seems to be the 

 most common condition, — and are left to float at the mercy of the winds 

 and waves. Other eggs, on the contrary, are laid in a common connecting 

 glutinous mass, like those of Lophius, Fierasfer, and others. In the former 

 genus the mass of eggs is very large ; in the latter, the number of eggs is 

 quite small. As far as protection to the young embryo is concerned, the 

 eggrs which are laid singly and are soon scattered far and wide would seem to 

 be in the best condition to escape their numerous enemies, while the large 

 masses of pelagic eggs, or those which are laid attached to the bottom in clus- 

 ters, would seem completely at the mercy of other Fishes, and of Crustacea, 

 Mollusca, Annelids, and other marine animals living upon animal food. 



All the eggs described in this memoir, — those without oil-globules as 

 well as those with them, — except when confined in masses, usually float 

 with the embryo down. Pelagic eggs are usually, as far as we have ob- 

 served them, perfectly transparent when first laid ; little by little, with the 

 formation of the embryo, chromatophores are formed, generally upon the 

 surface of the yolk-mass close to the embryo, or upon the embryo itself. 

 These chromatophores, at first colorless, then become pigmented, and while 

 the young embryo is still within the egg the characteristic pattern of color- 

 ation is often clearly indicated. They extend gradually over the whole em- 

 bryo, which, before the tail is well advanced, is usually completely covered 

 by characteristic pigment ; it is only with the growth of the tail that the 

 individual characteristics of coloration are plainly visible. (See the eggs of 

 Plates II., VII., X., XII., XIV., XVI.-XIX.) 



The yolk-mass, which in the earlier stages of the egg fills nearly the 

 whole outer envelope, is gradually resorbed with the formation of the em- 

 bryo. This resorption is very different in different species, and upon it 

 depends, of course, the size of the yolk-mass at the time the young fish is 

 hatched. (Compare PI. II. fig. 3, PI. 111. figs. S. !l. PI. X. figs. 4, 6, PI. XI. 



