ÖFVERSIGT AF K. VETENSK.-AKAl). FÖRHANDLINGAR 1894, N:0 10. 581 



compared witb tlie corresponding average relative measurements 

 of the plaice and the flounder. ^) Tlie length of head is rather 

 more than the average in the plaice. The depth of body is less 

 than in both parent-forms, and coraes nearest to Pleuronectes 

 cicatricosus. The minimum depth of body is a little larger than 

 the average for the plaice, but within the limits of its varia- 

 tions. Postorbital length of head is the same as in the plaice. 

 The distance between the anal fin and the tip of the snout 

 points to an intermediate character, quite remote from both 

 parent forms, but not so very difterent from that of Pleuronectes 

 cicatricosus. The middle rays of the caudal fin are long as in 

 the plaice, but the ventral and pectoral fins of this speciraen 

 resemble much more those of the flounder. 



The specimen above described is a female Avith large and 

 well developed ovary. 



As the plaice and the flounder are spawning at about the 

 same time and in the same localities, there is nothing, in re- 

 ference to time and place, to render the production of hybrids 

 impossible iior, considering how closely related they are to 

 each other, does it seem astonishing at all that such bastards 

 are produced. The fishermen even have observed them and 

 actually given them the narae of bastards. 



Plaice often varies in colour, as has been many times 

 pointed out by various authors. Specimens with their blindside 

 partially or wholly coloured and others with more or less of the 

 eyeside white are by no means very scarce in Cattegat. I have 

 seen several such varieties and I observed that in such cases it 

 usualiy was the hindpart of the body that had got the unusual 

 colouring or that was colourless. 



A specimen of plaice caught off" the shores of Bohuslän 

 1891 and now preserved in the University zoological Museum 

 at Upsala is almost wholly coloured with the exceptions of: the 

 head and the pectoral and the region above the pectoral on the 

 blind side. But it is anomalous in another respect, as well, 

 1) Conf. Smitt 1. c. p. 407. 



