ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 475 



is characterized by the presence of a middle cosmine-like layer, and 

 occurs only in the Chondrostei (Pal^oniscida3 and their allies) and in 

 the Polypterini ; while the latter variety — the Lepidosteoid scale — is 

 found in the Orders Amioidei (Protospondyli + Pholidophorid^e, and 

 01igopleuridffi)and Lepidosteoidei (Lepidosteidte and Aspidorhynchidai). 

 The Lepidosteoid scale is easily recognized by the absence of the middle 

 cosmiue-hke layer and by the presence of a system of delicate tubules 

 running through and at right angles to the bony layers. The tubules, 

 as a rule, branch only at their inner end, and pass outwards to the 

 surface. In the living tissue they are occupied by long protoplasmic 

 processes of large cells on the surface of the scale. Probably these 

 remarkable cells are merely modified bone-cells, which, instead of 

 becoming buried in the ostein matrix, remain outside it while retaining 

 their connexion, by means of the long process, with the place they 

 ori2:inallY held. 



Goodrich finds that the striking difference in the minute structure 

 of the true ganoid scales is also found in the cranial plates and other 

 dermal bones of these fishes. Thus, whereas Lepidosteoid tubules are 

 never found in any part of the skeleton of the Polypterini or Chondrostei, 

 they occur in the dermal bones of all the recent and extinct Amioidei 

 and Lepidosteoidei examined, with the single possible exception of 

 Oligo'pleurus. Moreover, not the dermal bones alone show the lepidos- 

 teoid structure, but the whole endoskeleton as well. The skull-bones, 

 the ribs, even the vertebral centra, are all provided with the characteristic 

 tubules traversing the bony lamellae. 



As a provisional hypothesis, the view may be adopted that the 

 Amioids and Lepidosteoids on the one hand, and the Teleosts on the 

 other, diverged from a primitive group (perhaps represented by OUgo- 

 pleurus) possessing Lepidosteoid scales and ordinary bone ; and that in 

 the former the Lepidosteoid structure spread inwards over the whole 

 endoskeleton. 



Luminous Organs of Lamprotoxus flagellibarba.* — C. L. Boulenger 

 describes the minute structure of the " luminous organs " of this inter- 

 esting fish which has a barbel many times longer than the body, a 

 peculiar looped band of luminous tissue on the anterior part of each 

 side of the body, a large photophore behind the eye, and small scattered 

 photophores besides. The scattered " grey specks " are luminous organs 

 of a very simple type, without lens or reflectors. The transparent cuticle 

 of the body is continued over the outer face of the organ to form a 

 cornea-like covering, whilst the embedded surface is backed by a dark 

 pigment layer continuous with that of the skin. Each organ is of the 

 nature of a small gland consisting of a small number of relatively large 

 cells of pyramidal shape, arranged radially with their narrower ends 

 meeting in the centre. There seems to be no central cavity. The 

 protoplasm of the cells is filled with granules ; the nucleus has an approxi- 

 mately central position. 



The " looped band " is a long cord partially embedded in the skin. 



* Scientific Investigations Fisheries Ireland, 1912 (published 1913) No. 2, 

 pp. 1, 2 (1 pi.). 



