FISH-CULTURAL INVESTIGATIONS AT ST. ANDREWS, SCOTLAND. 245 



the period at which the fishes ought to be freed; that is to say, whether they should 

 be placed in the sea just before the yolk-sac is absorbed or retained in large open-air 

 mclosures until they are adolescents. The difficulty of making - the inclosurcs pre- 

 cisely resemble the open sea in their pelagic fauna and flora (both of which are so 

 closely related to the well-being of the fishes) is well known; indeed, no perfect substi- 

 tute for the open sea can be found. Further experience, however, may enable us to 

 overcome many of these difficulties. 



III.— FURTHER REMARKS ON THE DEVELOPMENT AND LIFE-HISTORIES OF 

 THE FOOD-FISHES AT THE ST. ANDREWS MARINE LABORATORY. 



ON THE EGGS AND LARVAE OF THE POOR COD (GADUS MINUTUS). 



( 



Raffaele* briefly alludes to the egg and larva? of this species, which seems to be 

 one of the most ubiquitous gadoids, ranging from the Mediterranean to the INorth 

 Sea, remarking that the former (eggs) agree in general structure with those of the 

 cod, but that the larva' differ in the arrangement of the pigment. Marion t also found 

 a large number of ova in the Gulf of Marseilles, on the 7 th March, which he considered 

 were those of the capelan (Gad us minutws), aud he gives a figure of the larva. Lastly, 

 Mr. Cunningham states that in April he found this species ripe at Plymouth, the diam- 

 eter of the ova 1.02 mm., aud the peri vitelline space small. He did not hatch them. 



For several years the spawning of this species has been under consideration, but 

 a more or less complete account has only been obtained recently. In 1884 and 1885 

 many ripe females were seen, but no ripe male was available at the same time. By 

 the skill and care of a fisherman at St. Andrews (James Gourlay) numerous fertilized 

 ova were brought from the neighborhood of the Bell Bock in June last year (1802). 

 The nearly ripe ovarian egg has, as usual, a denser capsule, which, moreover, is 

 wrinkled. In diameter the ripe eggs ranged from -9900 mm. to 1-0287 mm., sizes 

 extending on both sides of the average given by Mr. Cunningham. And the series 

 of ova procured in the open sea off Aberdeen were from -9525 to*9906 mm., and were 

 thus somewhat less than the preceding. Only a very few reached 1*0287 mm. 



The development was comparatively rapid, as might have been anticipated in 

 the warm weather. Ripe ova fertilized at a. m. on the 0th June were in the multi- 

 celled condition at 5.45 p. m., with a well-marked perivitelline space. The temperature 

 at this period rapidly increased, so that considerable mortality ensued. Indeed, the 

 mere handling of the water containing them under the miscroscope killed the embryos, 

 Which on the 7th were outlined and the optic vesicles indicated. 



The eyes of the advanced embryos are silvery (one of the most characteristic 

 features of the egg), and yellowish pigment is scattered over the head, body, and yolk. 

 The young larva somewhat resembles the whiting in coloration and measures from 2-2 

 to 2*4 nun. The eyes are silvery greenish, and the entire head and body are dappled 

 with minute yellow specks, invisible under a lens, but seen by transmitted light 

 under a low power of the microscope. Black chromatophores occur along the ventral 

 border of the muscle-plates, the tip of the tail alone being free. A less distinct series 

 lies along the dorsal edge, and a few finely branched specks exist on the head. The 

 rectum terminates blindly at the posterior and upper part of the yolk, which seems 



* Mittheilungen Zool. Stat. Neap., vm Bd., 1 Heft, sep. ahth., p. 36, tav. i, f. 25, et tav. 2, pp. 20, 

 21, 1888. 



t Ann. du Musde d'Hist. Nat. de Marseilles, Zoolog., iv, p. 188, pt. 2, fig. 14. 



