THE THEORY OF DESCENT 257 



some probability, if there is some palaeontological evidence 

 in support of pure comparative anatomy ; and I also do 

 not hesitate to allow that such a statement would be of 

 a certain value with regard to a future discovery of the 



i 



" laws ' of descent, especially if taken together with the 

 few facts known about mutations. But it is quite another 

 thing with phylogeny on the larger scale. Far more 

 eloquent than any amount of polemics is the fact that 

 vertebrates, for instance, have already been " proved " to 

 be descended from, firstly, the amphioxus ; secondly, the 

 annelids ; thirdly, the Sagitta type of worms ; fourthly, 

 from spiders ; fifthly, from Limulus, a group of crayfishes ; 

 and sixthlv, from echinoderm larvae. That is the extent 



V * 



of my acquaintance with the literature, with which I do not 

 pretend to be specially familiar. Emil du Bois-Keymond 

 said once that phylogeny of this sort is of about as much 

 scientific value as are the pedigrees of the heroes of Homer, 

 and I think we may fully endorse his opinion on this 

 point. 



HISTORY AND SYSTEMATICS 



A few words should be devoted to the relations between 

 history and systematics in biology. Is there no contra- 

 diction between historical development and a true and 

 rational system which, we conceded, might exist some 

 day in biological sciences, even though it does not at 

 present ? By no means. A totality of diversities is 

 regarded from quite different points of view if taken as 

 the material of a system, and if considered as realised in 

 time. We have said that chemistry has come very near 

 to proper rational systematics, at least in some of its 



17 



