222 . THE BLENNY FAMILY. 



The ventral fins are now much smaller in proportion than in the 

 earlier stages, the rays may still be made out, though they are 

 evidently undergoing the transformation into the tactile organs 

 of the adult. They are scarcely smaller than in the adult, 

 though presenting more of their original character, i.e. that of 

 fins, with fin-rays and membrane. In the adult, as is well 

 known, they appear as a pair of tentacular organs. 



In the whole series may be noticed a proportionate decrease, 

 with age, of the eyes and pectoral fins, a very general character 

 in piscine development. The eyes are at first lateral but 

 gradually approximate to a dorso-lateral position, so that they 

 face upwards. The same change may be noticed in many of 

 the small littoral fishes (see Weever). 



We may observe that the viviparous blenny in common with 

 most fishes has in its young stages a continuous median fin 

 extending from the head backwards and round the tail 

 forwards to the vent. Unlike the majority of fishes, this 

 median fin does not break up into two or more dorsal fins, a 

 caudal fin and one or more anal fins, but retains its simple 

 larval continuity except a small dent in the posterior dorsal 

 region which indicates the line of demarcation between the 

 dorsal and the caudal. In its near ally, the shanny, as 

 mentioned, the caudal fin is quite free, and the dorsal shews 

 an indication of division into two, thus presenting an advance 

 upon this type. 



In estimating the age of this species at various stages, 

 matters are complicated by its viviparous habit. A young 

 blenny of 2 inches, newly ' born ' in January, has already lived 

 within its parent since the preceding summer and is probably 

 about 5 months old, although by customary usage it would be 

 termed ' one day old ' or even less. For comparison with the 

 oviparous types wc must consider this stage to be about 

 •5 months old and therefore the specimen 4| inches long 

 probably represents the size attained a little over one year 

 from hatching. 



A specimen killed by frost in St Andrews Laboratory in 

 February 1886 measured 10 inches, was full of young, and may 

 be reckoned as in its third year, about 2^ years old. 



