564 D. L. GAMBLE 



the parapophysis extends laterally past this point of union 

 (fig. 29 A, B, C). 



10. Between the dorsal and ventral cartilaginous rods of the 

 transverse processes and the dorsal and ventral rib heads in the 

 second and third vertebrae, procartilage cells persist which by 

 prohferation bring about the elongation of the transverse process. 

 In the trunk the tubercular head of the rib has no cartilaginous 

 connection with the rib-bearer, so this provision is necessary only 

 in the case of the parapophysis. 



11. The haemal-arch element (haemapophysis) appears as a 

 downgrowth from the base of the parapophysis. This growth 

 becomes dominant over the parapophysis which in the first tail 

 vertebra appears as a lateral process of the haemal arch (hae- 

 mapophysis) . It loses its connection with the haemal arch in the 

 second tail vertebra and appears as a lateral projection from the 

 notochord (fig. 28 B). 



CONCLUSIONS 



1. The dorsal shifting of the horizontal septum is the direct 

 cause of the change in rib attachment from the centrum to the 

 neural arch. 



2. That the rib is an independent element is indicated by: 



a. The apparent ease with which it loses its connection with the 

 parapophysis and becomes attached to the rib-bearer. 



b. In the very earliest stages the rib proton may appear in- 

 dependent of any vertebral element. 



3. Goeppert's belief that the rib never actually loses its at- 

 tachment to the basal stump is incorrect. In the second and 

 third vertebrae it has been seen that the rib connects with the 

 rib-bearer before this structure and the parapophysis (Goeppert's 

 basal stump) unite. 



4. The rib-bearer is not a dorsal upgrowth from the middle of 

 the basal stump, as Goeppert maintains, but is a chondrification 

 in the inner edge of the transverse septum which fuses with the 

 distal end of the parapophysis. As growth of the body takes 

 place, the distal end of the parapophysis elongates laterally 

 past this point of union. 



