DEVELOPMENT AND LIFE-HISTORIES OF TELEOSTEAN FISHES. 873 



appear to seek the tidal margin with great rapidity. The flounder and plaice are 

 probably the first to appear, the common dab being a little later. All the shallow sandy 

 flats round the British shores abound with young Pleuronectids. 



The Clupeoids of the first series appear in great numbers in the Bay in March, and 

 their presence corresponds with the period at which the hatching of the eggs of the herring 

 was accomplished in the laboratory. The comparative rate of growth was followed there- 

 after in the Bay throughout the summer months. Thus they measure about 7 mm. in 

 the early part of March, 12 to 15 mm. a month later, and in two months about 20 mm., 

 with a great increase in depth. In four months (i.e., from March) they reach 27 to 28 

 mm., though such may be small examples of this (the first) series. Those of the second 

 series occur in September and the following months. 



Though the differences existing between the larval herring and the larval sprat are 

 marked at the period of hatching, the former being a much larger and more active fish, 

 which soon gains strength to mount upward in the water, the latter being shorter and 

 furnished with a larger yolk, yet the rapidity in growth soon obliterates the most evident 

 features. Thus no bold line of distinction, as regards increase and safety, can be drawn 

 between these closely allied forms with their dissimilar eggs. Each is as prolific as the 

 other, and holds its own in every part of our seas. Much, no doubt, remains to be 

 discovered in this and similar cases of divergence of the ova of closely allied species, but 

 at present no general law can be laid down on this head, or in regard to the occurrence 

 of oil-globules. It is difficult to explain why the brill and Miiller's topknot should have 

 an oil-globule in their pelagic ova, and the turbot and " witch" be devoid of it. # 



The larval forms associated with the sand-eel occurred at the end of March, their 

 length being 6 to 7 mm. At the same time, however, larger forms were captured, viz., 

 18 to 25 mm. On the 14th April they had reached 8 to 9 mm., and at the end of the 

 month 14 mm. at most. On the 7th May others measured 27 mm., 10th July 33 mm., 

 and in August 45 mm. 



When placed under favourable conditions, there is no doubt young fishes grow 

 rapidly, as in the case of the viviparous blennies, which before leaving the ovary of the 

 adult reach the length of nearly two inches. 



While there is no difficulty in rearing large numbers of food-fishes to a certain stage 

 in the laboratory, it is probable that it would be most convenient, when stocking 

 certain bays, to place the larval fishes in the sea within a week, for thus they would be 

 furnished with more abundant, more varied, and more suitable food. Further, the intro- 

 duction of adults ready to spawn (e.g., soles) in suitable sandy bays, would probably be 

 found more economical than the method indicated, and they can be carried long distances 

 with ease and safety. The same remark applies to the herring, for adolescent examples 

 accustomed by degrees to fresh water, can thus be carried without injury to distant regions. 



* Mr Cunningham (op. tit., 1889, p. 48) has recently broached the hypothesis that the presence of an oil-globule 

 in the egg is connected with abundance of oil in the adult. This would not seem to suit in contrasting the turbot with 

 the brill, the cod with the ling, the bib with the gurnard, the dragonet with the rockling, &c. 



VOL. XXXV. PART III. (NO. 19 ). 6 T 



