E. LÖNNBERG, HYBRID GULLS. 



21 



of the head are also quite conspicuous, but not so dark. 

 The pattern of the back is very different in the downy 

 nestlings of L. marinus and L. glaucvs, in the former the 

 dark spöts are very distinct against the »stone-grey» ground 

 colour, while the latter only displays a slight dusky mottling, 

 the elements of which hardly take the shape of spöts except 

 to some degree on the wings. On the back of the hybrid 

 chick the spotted pattern is quite well developed, although 

 the spöts are not quite so dark as in L. marinus, but the 

 degree of distinctness of the spöts and the general appearance 

 of^the back of the hybrid chick offers quite a remarkable 

 resemblance to the corresponding condition of the nestling 

 of Larus argentatus^ 



Thus it may be stated as far as this single hybrid spe- 

 cimen is concerned that the spotted pattern of the back 

 (the marmw<?-character) proves to be dominant, and the non- 

 spottledness (the glaucus-charsiGter) recessive. The former is 

 also certainly more ancestral to its origin, and the latter 

 more csenogenetic. At the same time it may, however, be 

 observed that this spotted pattern shows a certain modifi- 

 cation to the more central stage displayed by L. argentatus. 

 This is of interest as its offers an analogy to the colour of 

 the mantle of the first hybrid generation (ef. above) as well 

 as to the pattern of the primaries of the sanae. 



The other specimen of the second hybrid or fa-generation 

 is about half grown. It is fuUy feathered except for some 

 remaining downs on the neck. It has no resemblance what- 

 ever with the corresponding stage of Larus glaucus, but 

 could with full right be taken for a young of L. argentatus 

 or L. marinus, more especially the latter in consequence of 

 the complete blackness of the primaries. 



In this case as well the paleness of Larus glaucus proves 

 thus to be a recessive characteristic, which, according to the 

 above expressed opinion about its most probably csenogenetic 

 nature, was to be expected. 



It is hardly possible to draw any more conclusions from 

 this material, and the result is somewhat meagre. It appears, 



^ If the hybrid nestling is placed side by side with a couple o/ nest- 

 lings of Larus argentatus, they are all of them so alike that they raight be 

 easily taken as belonging to the same hatch. ^ 



Arkiv för zoologi. Bd 12. N:o 7. 2* 



