NOTES ON TELEOSTEAN OVA AND LARVAE. 27 



little change in distribution. At 3 mm. length, for example, with the 

 yolk almost absorbed, the general arrangement of pigment is as above. 

 Head and body (except posterior extremity) appear of an almost 

 uniform bright yellow. In tlie anterior half of the post-anal region 

 the notochord shines white through the yellow, but in the posterior 

 part the yellow is so dense as to obscure it. The coloured pigment is 

 more concentrated on the head, along the dorsum, and about the rectum. 

 The fringe formed by the line of closely applied dendritic or pectinate 

 chromatopliores along the margin of the unpaired fins, has a some- 

 what brownish tint, which is not seen on other parts of the larva. 

 In the anal fin, the fringe begins some distance posterior to the anus. 

 Black pigment is most dense on the ventral surface at the level of the 

 pectoral fins and above the anterior part of the remains of the 

 yolk-sac, where the vestige of the oil-globule now measures about 

 0-03 mm. 



A larva in which the yolk had been fully absorbed (ca. 3 mm. long) 

 showed less distinctness as to the marginal pigment, and a concentra- 

 tion — more particularly of the black chromatophores — in the pigment 

 of the unpaired fins, about half-way between the anus and caudal 

 extremity. 



Eeticulate markings and small papillae on the epidermis are com- 

 monly found both in late embryonic and in larval stages. 



To summarize the main facts ascertained for Z. norvegicus: — The 

 spawning season, in the Plymouth neighbourhood, extends from April 

 to June, probably beginning somewhat earlier than the former month. 

 The pelagic eggs have a homogeneous yolk and a single oil-globule, 

 which is frequently of a greenish yellow tint. The average diameter 

 of the egg is 0"854 mm. in April and 0'817 nim. in May and June, the 

 limits lying between 0'75 and 0'90 mm. The oil-globule measures 

 0095-0"15 mm., the average diameter being 0"122 mm. Embryonic 

 yolk-sac and larval pigments are yellow (bright greenish yellow by 

 reflected light) and black, the former predominating and being visible 

 to the naked eye in the larva. The body and yolk-sac of the newly 

 hatched larva are rather elongate, the total length being about 

 2*58 mm. (Elirenbaum gives 2'52-2"76 mm.). The anus is situated a 

 short distance behind the posterior edge of the yolk-sac, and at about 

 ^ the body length from the snout. The characteristic feature of the 

 vitelligerous larva is the marginal pigmentation of the unpaired fins 

 and their total lack of pigment in tlie caudal region. 



