THE TRANSVERSE PROCESSES OF NECTURUS 543 



these ventral cartilages stains as deeply as that of the neural 

 arch, the lacunae are large and contain large cells. This is in 

 sharp contrast to the matrix of the lateral cartilage ('basal stump' 

 of Goeppert) which stains very faintly and gives every indication 

 of having been formed more recently. 



In the 5th, 6th, 7th, 8th, 11th, and 12th vertebrae the ventral 

 cartilages are entirely independent of the lateral cartilages (fig. 4) 

 but in the 9th, 13th, 14th, 16th, and 17th they are joined with 

 the bases of the lateral cartilages, from the proximal ends of 

 which they appear as ventral outgrowths (fig. 5, h.a.). These 

 elements are absent in the remaining trunk vertebrae, but in 

 several of these there is to be noted a shght tendency of the base 

 of the lateral cartilage to bulge downward. This possibly 

 locates the position of the ventral cartilage. It is seen that 

 anteriorly the greater number of the vertebrae possess separate 

 ventral elements, but that posteriorly the ventral and lateral 

 cartilages are joined. In several the ventral elements have lost 

 their identity entirely. 



These ventral knobs of cartilage were not observed by Goeppert 

 in Necturus, but he saw them in Salamandra ('96). Ventrad of 

 the slender bar of bone (fig. 1, &), which he interpreted as the 

 reduced basal stump, ventral cartilages were located which dis- 

 appeared at the onset of bone formation. Goeppert observes: 

 "There occurs in Salamandra an unhitherto described pecuharity. 

 On the ventral side of the notochord, cartilage elements are found 

 belonging to the haemal arch system. These are present in 

 the young animal. In the tail region they elongate to form the 

 haemal arches. There is no connection between the bony strand 

 of the rib-bearer and these elements. This separation must be 

 considered as a secondary condition." The way in which 

 Goeppert beUeves this separation comes about will be described 

 w^hen the vertebrae of the tail-trunk region of Necturus are 

 discussed. 



In a 30-mm. Polypterus larva Budgett ('01) found a meta- 

 meric series of cartilages resting upon the notochordal sheath. 

 There was a dorsal row, the bases of the neural arch, a lateral 

 row, forming the foundation of the transverse processes and ribs 



