846 STRUCTURE AND DEVELOPMENT OF LEPIDOSTEUS. 



Fig. 60. Diagram of the urinogenital organs of the left side of an adult female 

 example of Lepidosteus 100 centims. in length. This figure shews the oviduct (od) 

 continuous with the investment of the ovary, opening at oa into the dilated part of 

 the kidney duct (segmental duct). It also shews the segmental duct and the junction 

 of the latter with its fellow of the right side to form the so-called bladder, this part 

 being represented as cut open. The kidney (k) and lymphatic organ (/y).in front of it 

 are also shewn. 



PLATE 40. 



Fig. 61. Transverse section through the developing pancreas (/) of a larva n 

 millims. in length. 



Fig. 62. Longitudinal section through portions of the stomach, liver, and duode- 

 num of an embryo about a month after hatching, to shew the relations of the pancreas 

 (/) to the surrounding parts. 



Fig. 63. External view of portions of the liver, stomach, duodenum, &c., of a 

 young Fish, u centims. in length, to shew the pancreas (/). 



Fig. 64. Transverse section through the anterior part of the trunk of an embryo, 

 about a month after hatching, shewing the connection of the air-bladder with the 

 throat (a b'). 



Fig. 65. Transverse section through the same embryo as fig. 64 further back, 

 shewing the posterior part of the air-bladder (a b). 



Fig. 66. Viscera of an adult female, 100 centims. in length, shewing the alimen- 

 tary canal with its appended glands in natural position, and the air-bladder with its 

 aperture into the throat (a b'). The proximal part of the duodenum and the terminal 

 part of the intestine are represented as cut open, the former to shew the pyloric valve 

 and the apertures of the pyloric caeca and bile duct, and the latter to shew the spiral 

 valve. 



This figure was drawn for us by Professor A. C. Haddon. 



PLATE 41. 



Fig. 67. Transverse section through the tail of an advanced larva, shewing the 

 neural and haemal processes, the independently developed interneural and interhaemal 

 elements (is), and the commencing dermal fin-rays (df). 



Fig. 68. Side view of the tail of a larva, 21 millims. in length, dissected so as to 

 shew the structure of the skeleton. 



Fig. 69. Longitudinal horizontal section through the vertebral column of a larva, 

 5-5 centims. in length, on the level of the haemal arches, shewing the intervertebral 

 rings of cartilage continuous with the arches, the vertebral constriction of the noto- 

 chord, &c. 



Figs. 70 and 71. Transverse sections through the vertebral column of a larva of 

 5 '5 centims. The red represents bone, and the blue cartilage. 



Fig. 70. Through the vertebral region, shewing the neural and haemal 



arches, the notochordal sheath, &c. 



Fig. 71. Through the intervertebral region, shewing the intervertebral car- 

 tilage. 



