60 Prof. M'Intosli's Notes from the 



4. On the Post-larval Stage of Crystallogobius Nilssonii. 



In a fonner paper* an unknown elongated post-larval 

 form, with prominent teeth and long pectorals, procured on 

 the 20th July, 1889, was described, A further examination 

 of this young fish, which was only 7 millim. long, shows that 

 in all probability it is the post-larval stage of a male Crystallo- 

 gohius Nilssonii, which at that date had only once been found 

 in Scotland, viz. by Mr. Edward, in a rock-pool at Banflf. 

 The very early stage at which the special sexual characters 

 occur in this species is interesting ; yet Dr. Day considered 

 that in the young males the head is more pointed, indeed 

 almost as in the females, in which the jaws are short, straight, 

 and toothless. It is clear, however, that such a statement 

 requires amendment, especially the supposition that the teeth 

 (" canines ") are only developed as maturity is reached. In 

 the small example from St. Andrews it was the presence of 

 these characteristic teeth and the shape of the mandible that 

 attracted attention, and yet the larval marginal tin was still 

 present. The description given in the Ninth Report may be 

 supplemented by the remark that in the adult male the pectoral 

 tins are remarkable for their " broad (multiradiate) and some- 

 what lobate form, with their semicircular muscular root and 

 elongated roundish shape. When expanded the pectoral fins 

 are as deep as the body." In life they are boldly speckled 

 with black on a yellowisli ground, the latter being brightest 

 interiorly. The remarkable coloration of these fins in the 

 post-larval stage is an addition to the series in developing 

 Teleosteans. \Vhen the eyes of a fresh form are examined 

 from above they are finely iridescent and greenish blue ; even 

 when seen laterally they are silvery with a bluish sheen. 

 Since this specimen was captured Mr. Cunningham has pro- 

 cured many adults of both sexes near the Eddystone Light- 

 house, while Mr. Holt has been equally successful off the 

 west coast of Ireland and on the east coast of England. It 

 appears to be generally distributed round British shores, 

 though the adults have not yet been secured here. It is 

 sometimes found in as great abundance in Norway as in the 

 south ot England. The authors (Fries, Ekstrom, and Sun- 

 devali} of the recently published work on Scandinavian fishes 

 observe that June is approximately the spawning-season ot 

 this species, and the development of the post-larval example 

 would appear to point to May or early June as the probable 

 period on our shores. 



* Kinth Ann. IJepoit Fisheiy Btard lor Scotland, pt. iii. p. 332, 



