544 D. L. GAMBLE 



and a still smaller series of ventral cartilages forming the founda- 

 tions of the ventral ribs. He found all three series well developed 

 in the anterior region. The lateral series were developed out 

 into the horizontal septum as long processes, but at that stage 

 had no connection with the ribs which he saw forming inde- 

 pendently in the lateral portion of the horizontal septum, but 

 having no connection with the lateral cartilages. The ventral 

 series were also well developed and passed out between the ventro- 

 lateral muscles and the kidneys, never reaching, however, the 

 peritoneum at this stage. In the caudal region the lateral 

 series was not found and the ventral series had elongated to form 

 the haemal arches. 



Budgett stated in conclusion: ''In the possession of three 

 pairs of vertebrally placed cartilages resting upon the noto- 

 chordal sheath, before the commencement of bone formation, 

 Polypterus differs from all living vertebrates. " 



It is interesting to note that in the possession of these cartilages 

 the 21-mm. Necturus larva at this stage corresponds very closely 

 to Polypterus. Furthermore, cartilage is appearing in the rib 

 distally, apparently as it does in Polypterus. The difference 

 between the two forms lies in the fact that in Necturus the ventral 

 cartilages, in some of the trunk vertebrae, are joined with the 

 bases of the lateral cartilage and in the posterior trunk region 

 become more or less indistinguishable from them. In the tail 

 region this basal portion which represents ventral cartilage grows 

 down to form the haemal arch while in Polypterus the haemal 

 arch is formed by the ventral cartilages which have remained in- 

 dependent of the lateral cartilages throughout the trunk region. 

 In Polypterus the ventral cartilages are present throughout the 

 life of the individual and elongate to form the ventral ribs, while 

 in Necturus they disappear when bone formation begins. 



Salamandra, in so far as the ventral cartilages are concerned, 

 also corresponds closely to Polypterus. Here at an early stage 

 they are found in the trunk region and in the tail form the haemal 

 arch. Salamandra differs from Polypterus, however, in the loss 

 of the lateral cartilage. 



