ON A SPECIMEN OF HEMIDACTYLUS GLEADOVII. 31 



The scaling of the undivided proximal part, which for brevity will 

 henceforward be spoken of as the stump, is normal to this species of 

 Hemidactylus 1 ; while that of the ventral surface of the short branch 

 and of the dorsal surface and sides of both branches of the new growth 

 differs from the normal scaling. Now it is known that in the case of 

 certain lizards which have the power of renewing the tail after acci- 

 dental loss, the scaling of the new growth differs from the normal. 2 



The probability that the bifid portion of the tail in the present case 

 is a new growth was, therefore, suggested by the characters of the 

 scaling, and an examination of the internal structure left no doubt 

 on the point. It has long been known that the structure of the 

 renewed tail of a lizard differs remarkably from that of the congenital 

 tail, 3 and the subject has been recently exhaustively investio-ated by 

 Fraisse, 4 whose work includes an account of the renewed tail of 

 Hemidactylus. frenatus. The chief structural peculiarities of the 

 renewed tail were constant in the several genera he examined and may 

 be epitomised as follows : — 



(a) The vertebral column is not renewed as such, but from the 

 point of fracture an unsegmented, imperforate, and usually 

 somewhat irregular cartilaginous tube grows out in direct 

 continuation of the neural arches. This tube tapers with 

 the tail, and its lumen ends blindly near the tip. 

 (&) The spinal cord is not renewed, but the lumen of the 

 cartilage tube contains a core of connective tissue with 

 large blood vessels, which is continuous with the spinal 

 cord of the stump. In reality this core is a tube with 

 thick walls, as it contains a central lumen lined by a 

 single layer of columnar epithelial cells. This lumen is 

 continuous with that of the central canal of the spinal cord. 



(c) The innervation of the renewed portion is effected by 



infiltration of the spinal nerve roots from above the 

 point of fracture. 



(d) The caudal artery and vein of the stump grow into the 



renewed portion and give off branches within it. 



1 Boulenger, G-. A. Fauna of British India. Eeptilia and BatrachU, 1890, p. 87. 



2 Boulenger, G. A. On the scaling of the reproduced tail of Lizards, Proc. ZooL Soc 1888 

 p. 351. ' 



3 Duges, A. Memoire sur les especes indigenes du genre Lacerta, Ann. des Sciences 

 Naturelles, 1829, vol. XVI, p. 337. 



* Fraisse, P. Die Eegeneration von Geweben und Organen beiden Wirbelthieren, be- 

 sonders Ampbibien und Reptilien. Cassel, 1885. 



