1870-1S82] HYATT AND COPE 347 



clearly expressed letter. I have directed my publisher to Letter 256 



send you a copy of the last edition of the Origin, and you 



can, if you like, paste in the "From the Author" on next 



page. In relation to yours and Professor Cope's view on 



" acceleration " causing a development of new characters, it 



would, I think, be well if you were to compare the decapods 



which pass and do not pass through the Zoea stage, and the 



one group which does (according to Fritz M tiller) pass through 



to the still earlier Nauplius stages, and see if they present any 



marked differences. You will, I believe, find that this is not 



the case. I wish it were, for I have often been perplexed at 



the omission of embryonic stages as well as the acquirement 



of peculiar stages appearing to produce no special result in 



the mature form. 



The remainder of this letter is missing, and the whole of the last 

 sentence is somewhat uncertainly deciphered. (Note by Mr. Hyatt.) 



To A. Hyatt. * Letter 257 



Down, Feb. 13th, 1S77. 



I thank you for your very kind, long, and interesting 

 letter. The case is so wonderful and difficult that I dare not 

 express any opinion on it. Of course, I regret that Ililgen- 

 dorf has been proved to be so greatly in error, 1 but it is some 

 selfish comfort to me that I always felt so much misgiving 

 that I never quoted his paper.- The variability of these 

 shells is quite astonishing, and seems to exceed that of Rubus 

 or Hieracium amongst plants. The result which surprises me 

 most is that the same form should be developed from various 

 and different progenitors. This seems to show how potent 



1 This refers to a controversy with Sandberger, who had attacked 

 Hilgendorf in the Verh. der fihys.-med. Ges. zu IViirzburg, Bd. V., ami 

 in the Jahrb. der Malakol. Ges., Bd. I., to which Hilgendorf replied in the 

 Zeitschr. d. Deutschen geolog. Ges., Jahrg. 1877. Hyatt's name occurs 

 in Hilgendorfs pages, but we find no reference to any paper of this 

 date ; his well-known paper is in the Boston Soc. Nat. Hist., 1880. In a 

 letter to Darwin (May 23rd, 1SS1 ) Hyatt regrets that he had no oppor- 

 tunity of a third visit to Steinheim, and goes on : " I should then have done 

 greater justice to Hilgendorf, for whom I have such a high respect." 



: In the fifth edition of the Origin (p. 362), however, Darwin speaks of 

 the graduated forms of Planorbis multiformis, described by Hilgendorf 

 from certain beds in Switzerland, by which we presume he meant the 

 Steinheim beds in Wurtemberg. 



