The Newly- Hatched Larva. 7 



M'Intosh (1891) gives the diameter of the contained ova in spawn cast ashore 

 in St. Andrews Bay as 2'2860 mm., and of the large oil-globule as '5334 mm. For 

 an isolated pelagic egg captured about the same time in the Bay, he gives the 

 following dimensions :— long diameter, r6764: mm. ; short, r6383mm. ; oil-globule, 

 •3048 mm. 



Ehrenbaum (1905, 1911) records the diameters of the eggs of Lophius as varying 

 between 2' 13 and 2'36 mm., and of the oil-globules 0"53-0"57 mm. In his tables 

 for the determination of the plankton eggs of fishes occurring in the North Sea, 

 he gives the following criteria for the identification of the eggs of Lophius piscatorius : 

 — " Yolk homogeneous, without segmentation. Eggs enveloped in a common 

 mucous mass, from which, however, they often apparently become isolated. Eggs 

 polygonal, flattened against one another, with large perivitelline space." In view 

 of the foregoing observations, the last sentence should read : Mucous cells poly- 

 gonal, flattened one against the other, diameter of cell about twice egg diameter ; 

 egg free within the mucous cell, with small perivitelline space. 



The newly-spawned egg is entirely free from pigment, but even before the 

 embryo begins to assume definite form dark dendritic pigment appears on the em- 

 bryo and on the yolk in the neighbourhood of the embryo. Isolated eggs at this 

 stage of development are very easily recognised amongst the preserved material ; 

 the size of the egg and oil-globule, the thin membrane, and the pigmented yolk 

 and embryo, are sure guides for the identification of such eggs. 



As the embryo grows, the dark pigment rapidly spreads, but does not extend 

 to the tail of the embryo itself. The pigment becomes more intensive on the 

 head and anterior body portion, and appears as large, black, dendritic spots. The 

 dark pigment spots also spread down the food canal and over the yolk especially 

 in the neighbourhood of the oil-globule. Indeed, the pigmentation becomes so 

 dense over the oil-globule that the limpid colour of the oil is hidden and the oil- 

 globule seen through this veil of reticulated pigment appears as a cloudy-Uke 

 ball. 



Gradually the embryo assumes a more definite form. It always remains broad 

 and short, never extending more than two-thirds round the yolk. In isolated eggs 

 in the living state the black pigment appears very soft and delicate, and, in some 

 of the embryos, there is a development of violet pigment along the gut. This 

 violet pigmentation is not present in all specimens, and is often very transient, 

 disappearing from the embryo before it hatches out from the egg. Fulton (1902) 

 says that the newly-hatched larvae possess much bright canary-yellow in addition 

 to the black pigment. This canary-yellow pigment did not appear, however, in 

 any of these isolated eggs. 



The embryo almost fully grown and stretching two-thirds round the yolk causes 

 the thin membrane to stretch greatly by its violent movements within the egg. 

 Unhke most pelagic eggs, the embryo does not stretch round the whole circumference 

 of the egg before it is ready to hatch out, and the hatching may, therefore, take 

 place rather unexpectedly. Indeed, so pigment-free is the tail that careful obser- 

 vation has to be made to determine whether the embryos have hatched. There 

 is a very considerable amount of unabsorbed yolk still remaining when hatching 

 takes place. It is probably due to the fact that, by the embryo hatching out thus 

 suddenly, and remaining in the mucous cell for some considerable time before being 

 freed, differences in the description of the newly-hatched larva have arisen. 



Newly-Hatched Larva. 



{Fig. 3). 



The newly-hatched larva floats in the water with the yolk uppermost ; the head, 

 being heaviest, is lowest, so that the larva in still water assumes an oblique position, 

 the tip of the tail just touching the surface film. The newly-hatclied larva 

 is about 4"5 mm. long, and the yolk is still of enormous size in comparison, the 

 diameter being more than half the length of the larva. The pigment-free tail is 

 very short, being less than the diameter of the yolk. The larva is strongly pig- 

 mented with dense dark pigment, especially over the head. This pigment extends 

 over the body almost half way to the anus. The gut is also pigmented, and often 



