112 MR J. T. CUNNINGHAM ON THE 



a distance from the yolk, a preanal embryonic fin separating the two, as in the 

 herring. The notochord, however, is multicolumnar. As has already been 

 mentioned in the case of Esox, the preanal fin-fold extends between and in 

 front of the pelvic fins in the alevin of Salmo. 



The larva of Coregonus oxyrhynchus, Nilss., at different stages is figured by 

 Sundevall (loc. cit.). The ova were deposited from 6th to 10th November, and 

 hatched in the following February ; they fall loose and separate to the bottom 

 of the water ; the diameter measures 3 mm. The newly hatched embryo is 

 11 mm. long; the anus is near the end of the tail, far removed from the yolk 

 sac. The jtelvic fins develop at the sides of the preanal fin long before the 

 latter disappears, and the position of the pelvic fins is behind the anterior end 

 of the preanal fin, where it meets the yolk-sac. 



The ova of Thymallus (Grayling) are similar to those of Salmo, but smaller. 

 The ova of Osmerus {eperlanus at all events) are adhesive, the external adhesive 

 layer of the zona radiata peeling off from the inner, and forming a suspensory 

 membrane. Sundevall (Svensk. Akad., 1855) gives figures and description of 

 the newly hatched larva of Osmerus eperlanus; its length is 5 5 mm., the anus 

 is near the end of the tail, there is a single oil globule in the yolk, the eye is 

 slightly pigmented ; the eggs were obtained May 2, hatched May 20, 1855. 

 Agassiz and Whitman {Pelagic Stages, p. 38) remark that the development of 

 the pelagic egg they believe to be Osmerus mordax closely resembles that of 

 the herring as given by Sundevall. They seem to have overlooked Sunde- 

 vall's figures of Osmerus. The presence of an oil-globule in the larva of the 

 latter genus is sufficient to prevent its being confounded with the larvasup- 

 posed by the American authors to belong to Osmerus mordax. 



Fam. 16. Percopsid^e. 

 „ 17. Haplochitonhle. 

 „ 18. gonorhynchid^. 

 19. Hyodontid^e. 



Fam. 20. Pantodontid^e. 



21. osteoglosshle. 



22. Clupeid^e. 



The ova of Clupea harengus, Linn., have been carefully studied. The ova 

 are heavy and adhesive. The yolk is composed of a number of spherical or 

 nearly spherical yolk spheres, with no oil-globules. The blastodisc is large, 

 forming about one-fifth of the whole egg. The newly-hatched larva is pelagic 

 and very transparent, the anus is far behind the yolk sac, the notochord 

 unicolumnar, the eyes slightly pigmented, but no pigment in the rest of 

 the body. The fertilised eggs and larva? of Clupea sprattus, Linn., have never 

 been observed. Eggs, apparently mature, were pressed by Mr Duncan 

 M vithews from a few specimens of the fish which had well-developed ovaries. 



