798 STRUCTURE AND DEVELOPMENT OF LEPIDOSTEUS. 



converge in the caudal region, and form inferior arches, which 

 are not homologous with those of Selachii and Ganoidei, although 

 they also form spinous processes." 



The opposite view, that the haemal arches of the tail in Tele- 

 ostei contain parts serially homologous with the basal parts of 

 the haemal processes as well as with the ribs, has been also 

 maintained by many anatomists, e.g., Meckel, Aug. Muller, &c., 

 and has recently found a powerful ally in Gotte. 



In many cases, the relations of the parts appear to be funda- 

 mentally those found in Lepidosteus and Amia, and Gotte has 

 shewn by his careful embryological investigations on Esox and 

 Anguilla, that in these two forms there is practically conclusive 

 evidence that the ribs as well as the haemal costiferous pro- 

 cesses of Gegenbaur, which support them, enter into the forma- 

 tion of the haemal arches of the tail. 



In a great number of Teleostei, e.g., the Salmon and most 

 Cyprinoids, &c., the haemal arches in the region of transition 

 from the trunk to the tail have a structure which at first sight 

 appears to support Johannes Muller's and Gegenbaur's view. 

 The hsemal processes grow larger and meet each other ventrally; 

 while the ribs articulated to them gradually grow smaller and 

 disappear. 



The Salmon is typical in this respect, and has been carefully 

 studied by Gotte, who attempts to shew (with, in our opinion, 

 complete success) that the anterior haemal arches are really not 

 entirely homologous with the true haemal arches behind, but 

 that in the latter, the closure of the arch below is effected by the 

 haemal spine, which is serially homologous with a pair of coal- 

 esced ribs, while in the anterior haemal arches, i.e., those of the 

 trunk, the closure of the arch is effected by a bridge of bone 

 uniting the haemal processes. 



The arrangement of the parts just described, as well as the 

 view of Gotte with reference to them, will be best understood 

 from the accompanying woodcut (fig. 3), copied from Gotte's 

 memoir. 



Gotte sums up his own results on this point in the following 

 words (p. 138): "It follows from this, that the half rings, forming 

 the haemal canal in the hindermost trunk vertebrae of the Sal- 

 mon, are not (with the exception of the last) completely homo- 



