Maturation of the pelagic ovum of teleosteans, and its relation to certain phenomena in the life-history of the species

• Main Author: Fulton, Thomas Alexander Wemyss
• Published: University of Edinburgh 1897
• Online Access: https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.734881

The methods adopted in my investigations were as follows, (1) the examination of the immature and ripe ovaries in the living fish or in the fresh condition, without preparation, (2) the microscopical examination of parts of the fresh ovaries and of the intra-ovarian eggs at various stages, without preparation, in various media, (3) the study of stained and mounted sections of the ovaries and eggs prepared in the the usual way, (4) the determination in certain cases of the general nature and quantity of the intra-ovarian fluid present in ripening ovaries, (5) experimental observations on the physical properties of the opaque and the transparent mature eggs, and on some other points. The species whose ovaries and eggs have been investigated comprise the following : A. With Dispersed Pelagic Eggs : Grey Gurnard (Trigla gurnardus) | Red Gurnard (Trigla cuculus) | Lesser Weever (Trachinus vipera) | Mackerel (Scomber scomber) | Dragonet (Callionymus lyra) | Cod (Gadus morrhua) | Haddock (Gadus aeglefinus) | Bib (Gadus luscus) | Whiting (Gadus merlangus) | Saithe (Gadus virens) | Ling (Molva vulgaris) | Fourbearded Rockling (Motella cimbria) | Tusk (Brosmius brosme) | Halibut (Hippoglossus vulgaris) | Long Rough Dab (Hippoglossoides limandoides) | Turbot (Rhombus maximus) | Brill (Rhombus laevis) | Sail-fluke (Arnoglossus megastoma) | Plaice (PIeuronectes plati'ssa) | Lemon Dab (Pleuronectes microcephalus) | Witch (PIeuronectes cynoglossus) | Common Dab (Pleuronectes limanda) | Flounder (Pleuronectes flesus) | Sole (Solea vulgaris) | Solenette (Solea lutea) | Norwegian Topknot (Zeugopterwis norVegicus)| Sprat (Clupea sprattus) B. With Floating Eggs imbedded in Mucus : Angler, or Monk Fish (Lophius piscatorius) C. With Demersal Eggs: Short-spined Cottus (Cottus scorpius) Long-spined Cottus (Cottus bubalis) Pogge (Agonus cataphractus) Lumpsucker (Cyclopterus lumpus) Diminutive Sucker (Liparis montagui) Catfish (Anarrhichas lupus) Lesser Sand Eel (Ammodytes tobianus) Sparling (Osmerus eperlanus) Herring (Clupea harengus) The immature ovaries of the John Dory (Zeus father) and the common eel (Anguilla vulgaris) were also examined. The eggs of the Angler are pelagic in the sense that they float at the surface of the sea, but they are not separate and dispersed like ordinary pelagic eggs, being imbedded in a large quantity of mucus forming a long band which floats them; the eggs themselves are of the demersal type. ? The eggs of the John Dory have not hitherto been described; from a study of the features of the immature eggs they appear to be demersal. The ova of the eel and conger, according to the recent researches of Grassi,(29) are pelagic, as was previously surmised by Raffaele (64). Stained and mounted sections of the ovaries and intra-ovarian eggs of the following species were prepared and examined : - Haddock, Whiting, Bib, Grey Gurnard, Plaice, Lemon Sole, Flounder, Common Dab, Witch, Sole, Solenette, Norwegian Topknot, Long Rough Dab, John Dory, Viviparous blenny, Monk fish, arc. Common Eel. The eggs and portions of the ovaries of the following species were examined microscopically in the living or fresh condition in the ovarian succus, and in various media : - Cod, Haddock, Whiting, Ling, Saithe, Bib, Fourbearded Rockling, Gurnard, Red Gurnard, Turbot, Brill, Halibut, Plaice, Lemon Sole, Witch, Common Dab, Flounder, Sole, Solenette, Norwegian Topknot, John Dory, Lumpsucker, Catfish, Herring. The quantity and general character of the ovarian fluid was determined in the cod, ling, haddock, flounder, and plaice; by the courtesy of Professor Rutherford a special determination was made in the Physiological Department by Dr Milroy, with respect to the composition of the ovarian fluid of the plaice. Dr Milroy was also kind enough to investigate many other points of interest bearing upon my work, which are referred to later.