The Annals and magazine of natural history; zoology, botany, and geology . inprocess of atrophy, and may possibly be met with only in astate of perfect development in the fully gestated embryo,afterwards becoming resorbed. Fig. 2 shows the luminous organ in correlation with thesurrounding scales. From a bulbous centre, which latterrepresents the swelling seen in fig. 1, extend on two sidessome epithelial strands which are covered by pigment. These scales differ from the normal ones in the followingpoints:— (1) By having a more abundant pigmentation of theirpulpa, thus making the parts which th
The Annals and magazine of natural history; zoology, botany, and geology . inprocess of atrophy, and may possibly be met with only in astate of perfect development in the fully gestated embryo,afterwards becoming resorbed. Fig. 2 shows the luminous organ in correlation with thesurrounding scales. From a bulbous centre, which latterrepresents the swelling seen in fig. 1, extend on two sidessome epithelial strands which are covered by pigment. These scales differ from the normal ones in the followingpoints:— (1) By having a more abundant pigmentation of theirpulpa, thus making the parts which these organs occupy, andwhich are already prominent under ordinary macroscopicalobservation, more conspicuous. 562 Prof. R. Burckhardt on the (2) By having their apices blunter than is the case withthe normally constituted scales, in particular those rows ofscales which are situated orally with respect to the luminousorgans. (3) By their base not terminating in a simple rhomboidaledge, but possessing finger-shaped projections which securefor these organs a firmer Scale-bases and pigment of the luminous organ of L. rostratus. In Lcemargus borealis the luminous organ appears to havearrived at a stage of further reduction because its histologicalstructure is more vestigial still than is the case with thatdescribed by Johann. Besides this, the scales which surround the luminous organsof this species differ from the normal ones in their strongerpigmentation only and in being more crowded, but not invariety of form. Luminous Organs of Selachian Fishes. 563 I will now proceed to the description of the topographicaldistribution of these photogenic organs, concerning which itshould be said that it differs in every species. In the genus ftpinax these organs were discernible, besidesin S. niger, in and S. granulosus, of which latter thetype is preserved in the British Museum, [npusillus they aredistributed in an almost identical manner to those in S. niger,i. e. the whol
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