PHYLOGENY. 85 



have no clavicle, a bone which is possessed by the 

 latter, it is only to be concluded that the early lemur- 

 oids were derived from Condylarthra which possessed 

 a clavicle. And in the discussion of the descent of 

 one order from another, care must be taken that fam- 

 ily, generic, and even specific characters are not im- 

 ported into the discussion. 



It is this confusion of ideas on the part of both 

 phylogenists and their critics, that has brought phylo- 

 genetic schemes into a discredit in some quarters, 

 which is sometimes deserved and sometimes unde- 

 served. Embryologists are especially apt to construct 

 impossible phylogenies, as they are generally not sys- 

 tematists, and frequently not anatomists. An excel- 

 lent illustration of an impossible phylogeny is that of 

 the fishes published a few years ago by the embryolo- 

 gist Dr. Beard. As an illustration of clean-cut phy- 

 logeny without confusion, I cite that of Haeckel ; which 

 I have shown to be, as regards the Vertebrata, mainly 

 correct. 



In attempting to ascertain the course of evolution 

 of the Vertebrata, and to construct phylogenetic dia- 

 grams which shall express this history, among the dif- 

 ficulties arising from deficient information one is espe- 

 cially prominent. As is well known, there are many 

 types in all the orders of the Vertebrata which present 

 us with rudimentary organs, as rudimental digits, feet 

 or limbs, rudimental fins, teeth, and wings. There is 

 scarcely an organ or part which is not somewhere in a 

 rudimental and more or less useless condition. The 

 difficulty which these cases present is, simply, whether 

 they be persistent primitive conditions, to be regarded 

 as ancestral types which have survived to the present 

 time, or whether, on the other hand, they be results of 



