BDELLOSTOMA DOMBEVI, LAC. 147 



are distributed between the males, females and hermaphrodites 

 in the manner indicated by the following table : 



Of loi individuals having 1 1 



gills on both sides, . 61 were males, 37 were females, and 3 hermaphrodites. 

 Of 26 individuals having 1 1 



gills on one, 12 on the 



other side, . . . 14 " " 12 " " " o " 



Of 163 individuals having 12 



gills on both sides, . 94 " " 66 " " " 3 " 



Of II individuals having 12 



gills on one side and 13 



on the other, . . 8 " " 3 " " " o 



Of S individuals having 13 



gills on both sides, • 5 " " 3 " '' " o 



Totals, 182 121 6 



The sexuality of the Bdellostoma does not appear to depend 

 upon size or age, for of 10 small individuals (under 15 inches) 

 there were 7 males with gills, \%, 2 females with gills, l|, and 

 I female with gills, \\. 



Of 1 5 large individuals (over 20 inches) there were 8 males 

 with gills, i|, I female with gills, 1|, 5 males with gills, \\, 

 and I male with gills, l|. 



In 1875, Anton Dohrn, the founder and talented director 

 of the Zoological Station of Naples, first clearly defined the 

 hypothesis of degeneration, and fully illustrated its application 

 to the vertebrata in his famous paper, " Origin of Vertebrates." 

 Dohrn corrected the then prevalent ideas, according to which 

 all the simpler forms of animals, anatomically considered, were 

 to be looked upon as more primitive and as representing 

 ancestral stages in the development of the groups to which 

 they belonged. He was not fortunate in his selections of 

 cases of degeneracy among vertebrates, as I hope to make 

 clear to you. As a typical case of true degeneracy we have 

 the well-known case of the Tunicate, which during its devel- 

 opment passes through a stage which, according to the 

 '' biogenetisches Grnndgesetz'' must be considered to be strictly 

 vertebrate in its morphological characters. These vertebrate 

 characters are not retained by the Tunicate, however, but are 

 absolutely destroyed during the growth of the larval body, so 

 that in the adult condition there is nothing left to ever remind 



