^80 THE PAXORPOiD COMPLEX (Introduction), 



forms a very generalised statement covering a very much wider 

 field than the original one, and open to far graver objections. 

 As regards Law No. 1, this can only be accepted as true in its 

 very widest sense, i.e., that there must be pre-existing living 

 material, or cells, as a basis from which any new structure is to 

 be developed; and, in that sense, it ceases to have any value, 

 and becomes a truism. With respect to Law No. 2, this ceases 

 to be true when the restrictions contained in the original state- 

 ment of the law are removed. To mention only one obvious 

 example. The thoracic legs of certain Hymenoptera (e^g , Chali- 

 codoma) appear in the embryo; they then disappear throughout 

 larval life, but reappear again in their complete form in the 

 imago. Thus, in this case, as in many others, "a lost organ is 

 regained"; and a bald statement to the contrary is not only not 

 a law, but it is not true. Moreover, it may not be argued that 

 the law is true when applied to Phylogenetic problems only, and 

 not to Ontogeny. For, if there is any truth in the Biogenetic 

 Law at all, it is certain that what occurs in Ontogeny is of the 

 same nature, and governed by many of the same laws, as what 

 occurs in Phylogeny; and if we frequently find that lost organs 

 are regained in the course of Ontogeny, then it follows that we 

 may by no means assert that the same possilnlity cannot hold 

 for Phylogeny. With respect to Law No. 3, it is only necessary 

 to remark that there is probably no Phylum in which rudiment- 

 ary organs are so often redeveloped as in the Arthropoda, and 

 that this is particularly true of appendages. 



It would seem much wiser to do without any attempt to formu- 

 late laws (so-called) for the solving of Phylogenetic problems, and 

 to treat each case, as it presents itself, upon its own merits. In 

 most cases, for instance, it is quite capable of definite proof that, 

 in a given phyletic series, an organ originally present has been 

 lost, and never regained in any of the descendant genera. In 

 other cases, not so numerous it is true, it is capable of proof, by 

 reference to palaiontological evidence, that lost organs have been 

 regained, or, perhaps, that organs which, on the strict applica- 

 tion of Law No. 2, would have to be regarded as originally pre- 

 sent and subsequently lost, are really new developments not 



