582 LÖNNBERG, OBSERVATIONS ON CERTAIN FLAT-FISHES. 



for it is rachitic. Tlie spiiie just beliind tlie skull lias probably 

 been broken or damaged while at a juvenile stage. The result 

 of this has been an upward curve of the spine and tlie vertebrfe 

 in consequence are shorter but thicker. This curve of the spine 

 has even had an influence upon the exteriör of the body. It is 

 thicker than ordinarily and the anterior curve or profile of the 

 back has got steeper. Whether this deformity of the spine has 

 any connection with the colouring of the blind side is of course 

 not easy to say, but T suppose that such is the case as the 

 deposition of pigment depends, to a certain extent. upon the 

 sensibility of the nerves ^) especially in the flounders. That part 

 of the body, which gets innerved from the medulla behind the 

 rachitic portion is darkly coloured with pigment. 



In the middle of June when I was about to leave Lands- 

 crona I obtained a very peculiar flounder the measurements of 

 which are given in table 3. It was caught off Anholt and was 

 unknown to me as regards both colour and shape etc. Its 

 colour was a kind of undefined bluish brownish gray and quite 

 even, without any spöts. Thus it was easily seen and I picked 

 it out from among several hundred plaice. Wlien I asked the 

 fishermen whether they had seen a lish of that kind before, they 

 declared they had not; someone however expressed it as his opi- 

 nion that the fish was "a cross between a plaice and some other 

 flounder possibly a dab or a pole, he could not say which."' I quote 

 this opinion as it was not very unlike my own when I first saw 

 the fish in question, for I did not think of the dab as being 

 likely, but of the pole (Pleuronectes cynoglossus) and I will give 

 my reasons. The form under consideration is very closely related 

 to the plaice and that that species must be counted among its 

 parent forms is quite certain. This may be seen in many cha- 

 racteristics; among others worthy of mention is the presence of 



*) An example of suoh an occurrence is afforded by the case of a pike, whose 

 upper jaw got broken and bent upwards, its tongue and mouth (whicb is 

 ordinarily colourless) as far as the aecident had exposed them to the light» 

 were coated with pigment. The specimen spöken of was captured in Upland 

 and is now preserved in the Upsala Mnseum. 



