Miss Agnes Crane — Evolution of the Bvacldopoda. 71 



I have seen no reason to change the opinion, strongly expressed in 

 1881, that where the Brachiopoda go the Polyzoa must follow (16). 

 A parallel arrangement of the simpler hingeless forms with the 

 inferior Polyzoa — a very instructive and significant series — reveals 

 60 many anatomical points in common that it is diflScult to affirm 

 any closer relationship. Milne-Edwards' name may still be retained 

 for this group, from which, however, the Tunicata have been almost 

 unanimously ejected. Conchologists have an inveterate habit of 

 figuring the shells, from the physiologist's point of view, wrong 

 way up.' If we turn the Lingida right side up we see at once the 

 resemblances to the inferior class of moss-animals. 



The possibility of demonstrating descent with modification among 

 the Brachiopoda, so numerous in form and so persistent a race of 

 organisms, early attracted the attention of Darwin. He was much 

 struck with a series of Spiriferce which had been arranged on a 

 tablet to illustrate the succession and variation of species of that 

 genus by Mr. J. W. Salter, Palfeontologist of Her Majesty's 

 Geological Survey, in the Jermyn Street Museum. 



Since these lines were written a fui'ther instalment of Hall and 

 Clai'ke's great work on the Palaeozoic Brachiopoda has been issued 

 (38, 39). By a singular coincidence I find that these authorities 

 therein propose a classification of the numerous species of the genus 

 Spirifer into six sections or groups of species, according to their 

 external ornamentations and because it serves to indicate within 

 the integrity of the genus lines of progress leading to resultants 

 which are no longer congeneric. In other words, specific valuations 

 among the Spirifers lead up to the evolution of other spire-bearing 

 genera. 



It is now more than thirty years ago since Darwin first addressed a 

 letter to Thomas Davidson, historian of the British Fossil Brachiopoda, 

 suggesting that " no one could work out the subject better than he." 

 "I am inclined to suspect," he wrote, in April, 1861, "that on the 

 whole the evidence of the Brachiopoda would be favourable to the 

 notion of descent with modification. Many curious points would 

 occur to anyone thoroughly instructed on the subject who could 

 consider a group of beings under the point of view of descent with 

 modification" (p. 24; 29). 



" Mr. Davidson is not at all a full believer in great changes of 

 species, which will make his work all the more valuable," wrote 

 Darwin subsequently, with characteristic fairness, to Eobert 

 Chambers, author of "The Vestiges of Creation." The corre- 

 spondence between Davidson and Darwin on this subject was 

 afterwards published in "The Life and Letters of Charles Darwin," 

 edited b}' his son, Francis Darwin, and will be found on pp. 366-367 

 of the second volume of that most interesting record. 



In 1876 Davidson published a French edition of the excellent 



^ I am glad to note that Prof. Alpheus Hyatt has reversed all the figures of the 

 illustrations to his remarkable memoir " Phylogeny of an Acquired Characteristic," 

 a powerful argument opposed to the Weismannian hypothesis, issued in the Pro- 

 ceedings of the American Philosophical Society, vol. xxxii. No. 143. 



