220 Mr. E. Shann on the Life-history and 



appear in 4 ram. specimens, but these fins are not well deve- 

 loped till 5-5'5 mm. is reached. In most 4 mm. specimens, 

 too, the otolith and the nasal aperture can be clearly distin- 

 guished, the former in a median position slightly anterior to 

 the gill-slit, while the latter is placed midway between the 

 eye and the point of the snout. By the time 4*5—5 mm. is 

 reached all trace of the yolk-sac has disappeared, and this 

 point in the development may be said to mark the transition 

 from the larval fo the postlarval condition. The spiny dorsal 

 and ventral fins appear in forms from 6'5— 7 mm. In the 

 anterior portion of a 7 mm. specimen, depicted in PI. IX. 

 fig. 3, the. fused ventrals can be seen slightly posterior to the 

 gill-slit. In the same figure the fore, mid, and hind brain 

 are clearly shown ; the otolith has approached nearer to the 

 eye than was the case in the larval forms ; the nasal aperture 

 can be seen slightly above the line joining the centre of the 

 eye to the point of the snout ; the teeth are well developed, 

 and the highly inclined mandible is characteristic of gobies 

 of this size. The eye throughout the larval and most of the 

 postlarval stages is lateral in position, but at 10—12 mm. it is 

 found in the dorso-lateral position which it retains throughout 

 the remainder of the life of the fish. The latter position is 

 attained by a gradual vertical displacement. In forms from 

 6-7 mm. the posterior extremity of the notochord is curved 

 sharply upwards, and the hypural bones of the tail can be 

 clearly distinguished with the aid of the microscope (see 

 PI. IX. fig. 2). The caudal fin-rays are sixteen in number, 

 and thereafter increase in size but not in quantity. 



About 12 mm. the outward appearance of the adult is 

 assumed, and the gobies may thenceforward be described as 

 young, in contradistinction to the postlarval. A specimen 

 40 mm. in length was captured at St. Andrews towards the 

 end of April, another 32 mm. at Station V., Firth of Forth, 

 early in February, and eight averaging 34 mm. off Aberdeen 

 in the middle of May. All these were young gobies ap- 

 proaching the end of their first year of growth, and with it 

 sexual maturity. Six specimens averaging 53 mm. were 

 procured at St. Andrews in August, five averaging 50 mm. at 

 Station V., Firth of Forth, in October, and one 60 mm. off 

 Aberdeen in the middle of May. All these specimens were 

 fully adult. Thus it may be concluded that sexual maturity 

 is reached in G. minutus when the individual has attained a 

 length of not less than 45 mm., or, roughly, after the termina- 

 tion of twelve months' growth. In corroboration of this 

 statement the following paragraph may be quoted from the 



