Holt — On the Eggs and Larvce of Teleosteans. 461 



of S. variegata is 1-36 mm.). The shape is usually spherical, but some are ovoidal, 

 having a long and short diameter of "SSo and -775 mm. respectively. The 

 numerous small oil-globules (o. g.) are restricted to the vegetative hemisphere, 

 both in early (fig. 10) and advanced (fig. 9) stages, and are never aggregated at 

 the sides of the embryo or under it, as in <S'. vulgaris. 



The globules are much larger than those in the unfertilized egg of *S'. vulgaris, 

 and are quite colourless. There is a cortical layer of yolk segments {c.v.) very con- 

 spicuous in the early ova,* but becoming less so as development proceeds, though 

 they are still visible in the early larva (fig. 46). 



Raffaele {op. cit., p. 64) describes and figures a pelagic egg, his undetermined 

 species 2, which presents the closest possible resemblance to this form. Its diame- 

 ter is •75 mm., thus differing very slightly in size from our form. It occurs at 

 Naples sparingly in January ; I think it more than possible that the two forms 

 are identical, the resemblances outweighing the slight discrepancy in size. 



The period of development in ovo, in the form before us, occupies about five 

 days. The embryo is at first colourless, but pigment of a faint yellow colour, 

 black by transmitted light, appears with the first development of the free caudal 

 region (fig. 9). 



It occurs in small rounded chromatophores on the top of the ej'es and head, in 

 a double line along each side of the trunk, and over the general surface of the 

 yolk-sac. At this stage the otocysts have not appeared, and the lenses are not 

 invaginated. 



As development proceeds the pigment gains in brilliancy, becoming in the 

 larva a bright-orange, brown by transmitted light. 



The larva emerges at an early stage of development (fig. 46). The yolk (?/.) 

 is large and globular, there is no mouth, and the fore-brain is bent down to the 

 anterior extremity of the yolk-sac. The olfactory apparatus cannot be made out ; 

 the eyes are of moderate size, and pigmentless, save for a few chromatophores over 

 the retina. The otocysts (oi.) are small and oval, and remote from the eye. The 

 contour of the head is rounded, and the medulla rises somewhat above the plane 

 of the top of the mid-brain. The cerebellum is somewhat large, but the pineal 

 body is not visible. 



The heart (h.) lies immediately behind the eyes, in a depression of the top of 

 the yolk. It is partially constricted into auricle and ventricle, and is, as usual, 

 directed to the left. 



* These segments appear first at the animal pole, Ipeneath the blastoderm, and extend gradually over 

 the whole periphery of the yolk. A very early ovum, -which I obtained at St. Andrews on the 30th of 

 July, showed the oil-globules mostly arranged in a ring at the rim of the vesicular layer, which did not 

 quite reach the equator. Their subsequent disposition may be in some way due to the extension of the 

 segments, 



3 T 2 



