340 STKUCTURE OF THE LARVAL POLTPTEEUS. 



PLATE XXXIII. 



Fig. 1. A side view of a reconstruction from transverse sections, 10 f* in thickness, of the ri|jht 

 half of the primordial cranium and visceral arches of the larval Polypterus. The great 

 afferent and efferent blood-vessels to the external gill are also shown. The last section 

 of the reconstruction cuts off the exoccipital region, the third and fourth branchial 

 arches, and the afferent and efferent vessels to the external gill. 



Fig. 2. A posterior view of the same, reconstructed. The cut surfaces of the cartilage where 

 the reconstruction ends posteriorly are dotted. The anterior region of this reconstruction 

 has also been cut off just behind the nasal capsules. 



Fig. 3. Anterior aspect of the same. The cut surfaces are dotted. The portion reconstructed is 

 the same as for fig. 2. 



Fig. 4. Reconstruction of the left side of the occipital region and anterior end of the vertebral 

 column, showing that the exoccipital cartilage has still the form of a neural arch, though 

 already fused to some extent above and below with the cranium. The lateral and ventral 

 processes are seen to be very long in this region. The parachordal cartilages are shown 

 to send a bridge of cartilage under the aorta. 



Fig. 5. A dorsal view of a reconstruction of a portion of the mid-region of the vertebral column '. 

 The dorsal spines have been cut off. 



Fig. 6. Reconstruction of the caudal portion of the axial skeleton showing the form of the neural 

 and ventral arches at this stage and the manner in which the anal fin is supported ; also 

 the very slight upward tendency of the termination of the notochord. 



Fig. 7. Reconstruction of the cartilage of the left half of the shoulder-girdle, seen from behind. 



Fig. 8, Reconstruction of the shoulder-girdle and left pectoral fin, seen from the front, showing 

 the great length of the metapterygium as compared with that of the propterygium and 

 the formation of the radials from one continuous plate of cartilage. 



(Fig. 8 of this Plate is X 20 ; all the other figures are x 30. ) 



' The anterior end of this portion is to the right. 



