Rate of Groivth in Gobius mi nut us. 237 



It will be seen from the above table that though the fishes 

 were arranged in order of their respective lengths, the series 

 of dates of capture falls into a natural sequence of itself. 

 Further, that fishes of different lengths captured on the same 

 date show a marked agreement in the structure of their 

 otoliths. Another point in support of the age-determination 

 by this method is the fact that the average diameter of the 

 otolith, or part of an otolith, bordered by the first dark (thin) 

 band is practically constant. From this it may be inferred 

 that, at the end of the first winter's growth, the otolith of 

 G. minutus reaches an approximately constant size ; hence, 

 that markings of the otoliths are at least an approximate clue 

 to the age of the fishes which bear them. It will be seen 

 from the drawings that the outline of the otolith is at first 

 circular, but undergoes a series of changes by which it 

 assumes the form of an irregular polygon, and finally in 

 80 mm. forms becomes roughly rectangular. In this con- 

 nexion it is noteworthy that in several specimens about 65 mm. 

 the otolith outline formed an almost regular pentagon; this 

 is well shown in PI. X. fig. 13. 



Some Additional Notes on G. flavescens, Fabr. 

 (plim ruthensparri). 



The breeding-season of this species continues over a con- 

 siderable period — that is to say, from April or M ly to the end 

 of August. In marked contrast to G. minutus, however, the 

 young of very varied sizes, and probably of different ages, 

 live together in shoals. This fact renders a definite idea of 

 the rate of growth of the species almost impossible. In a 

 haul made in Loch Gilp on 31/10/99 upwards of forty speci- 

 mens of G. flavescens were taken, and these ranged in size 

 from 12'5 to 27*0 mm.; moreover they formed a uniform 

 series, the largest gap in which was 1*5 mm. In the same 

 haul were four specimens ranging from 31*5 to 36 mm., and 

 these differed very little in aspect from the largest of the 

 fir3t-mentioned series. In another haul made in the S.E. 

 corner of St. Andrews Bay on 1G/9/89 upwards of fifty 

 specimens were taken, and these formed a series, with scarcely 

 a break, from 9 to 32*5 mm. On 5/11/97 in Bressay Sound 

 a series was obtained ranging from 20 to 32 mm. It was 

 possible to make out the structure of the otoliths of the latter 

 fishes, and they showed a dense growth surrounded by a 

 thinner growth, indicating that the fishes were entering upon 

 a period of retarded growth. All that can be stated with any 



