EVOLUTION WITHIN HIGHER PHYLA 33 



since the historic point of view was adopted by the 

 naturalist as the outcome of Darwin's teaching, and 

 the zoologist may safely claim that his method, confirmed 

 by palaeontology so far as evidence is available, may 

 be extended beyond the period in which such evidence 

 is to be found. 



And now our last endeavour must be to obtain some 

 conception of the amount of evolution which has taken 

 place within the higher Phyla of the Animal Kingdom 

 during the period in which the fossiliferous rocks were 

 deposited. The evidence must necessarily be considered 

 very briefly, and we shall be compelled to omit the 

 Vertebrata altogether. 



The Phylum Appendiculata is divided by Lankester 

 into three branches, the first containing the Rotifera, 

 the second the Chaetopoda, the third the Arthropoda. 

 Of these the second is the oldest, and gave rise to the 

 other two, or at any rate to the Arthropoda, with which 

 we are alone concerned, inasmuch as the fossil records 

 of the others are insufficient. The Arthropoda contain 

 seven Classes, divided into two grades, according to the 

 presence or absence of antennae 1 — the Ceratophora, con- 

 taining the Peripatoidea, the Myriapoda, and the Hexa- 

 poda (or insects) ; the Acerata, containing the Crustacea, 

 Arachnida, and two other classes (the Pantopoda and 

 Tardigrada) which we need not consider. The first 

 Class of the antenna-bearing group contains the single 

 genus Peripatus — one of the most interesting and ancestral 

 of animals, as proved by its structure and development, 

 and by its immense geographical range. Ever since the 

 researches of Moseley and Balfour, extended more re- 

 cently by those of Sedgwick, it has been recognized 

 as one of the most beautiful of the connecting links 

 to be found amongst animals, uniting the antenna-bearing 

 Arthropods, of which it is the oldest member, with the 

 Chaetopods. Peripatus is a magnificent example of the 

 far-reaching conclusions of zoology, and of its superiority 



1 The so-called antennae of Crustacea are developed very differently 

 from true antennae. 



POfLTON 



