60 On the Nature of ‘ Hemapophyses.” 
XVI.—On the Nature of ““ Hemapophyses,” in reply to some 
Criticisms of M. Dollo. By G. A. BOULENGER. 
In two papers published in the ‘ Bulletin scientifique de 
France,’ xxiv. 1892, of which extracts have been kindly sent 
me by the author, M. L. Dollo has endeavoured to show 
that his maxim, ‘‘ Chez tous les vertebrés, les cétes sont homo- 
logues aux cétes et les hemapophyses aux hemapophyses,” 
being true, the views I have expressed as to the nature of the 
Reptilian chevrons are necessarily incorrect. I fear my friend 
lets himself be carried astray by theories which, however 
fascinating they may appear when treated in the talented 
manner with which all readers of his works are familiar, are, 
in this special case, unsupported by facts. I maintain that 
there is not at present the slightest evidence that the chevrons 
are homologous throughout the Vertebrata, as my critic will 
have it, An examination of the vertebral column of Amia 
suffices to show how, in that type, the true ribs gradually 
converge ventrally towards the caudal region, and do duty 
for the ‘ hemapophyses.” The embryological researches of 
C. Scheel (Morphol. Jahrb. xx. 1893, p. 1) also prove that in 
the Teleoste1 the hemapophyses are formed by the parapo- 
physes or parapophyses and ribs. It further appears to me 
that M. Dollo, when writing on the subject, had not present 
to his mind the multitudinous modifications of the vertebral 
column of Teleosteans, for I cannot see how his account of 
the relations of the ribs and hemal arch can be reconciled 
with the structure of such a well-known type as the typical 
Scomberoids, Mackerel or Tunny. 
I here quote Cuvier on the Mackerel :—“ L’épine a trente 
et une vertébres, ...... Les apophyses transverses forment 
Vanneau [hemapophysis] dés la dixiéme. Elles ont d’abord 
deux cotes de chaque cété, partant du méme point ; ensuite 
les cétes se séparent un peu. Les supérieures, plus courtes, 
durent jusqu’a la dix-huititme vertébre; les autres, plus 
longues, cessent dés la treiziéme.’’ Hence we have on one 
and the same vertebra (10th to 13th) the two ribs, assumed 
by M. Dollo to represent the true rib and the hemapophysis, 
in addition to the hemal arch. 
A further argument against M. Dollo’s theory of the 
homology of the hemal arch throughout the Vertebrata is 
derived from the fact that in certain Cyprinoids the anterior 
thoracic vertebrae possess a ventral arch enclosing the aorta. 
This arch is pronounced by Scheel to be formed by mere 
fibrous processes of the centrum, and to be homologous with 
the chevrons of Urodele Batrachians. 
