I87Q.J DR. GUNTHER'S HELP. 303 



have cost me infinite time, and heaven knows when I shall 

 have all my MS ready ; but I am never idle. 



C. Darwin to A. Gilnther. 



May 15 [1870]. 



MY DEAR DR. GUNTHER, Sincere thanks. Your answers 

 are wonderfully clear and complete. I have some analogous 

 questions on reptiles, &c., which I will send in a few days, 

 and then I think I shall cause no more trouble. I will get 

 the books you refer me to. The case of the Solenostoma * is 

 magnificent, so exactly analogous to that of those birds in 

 which the female is the more gay, but ten times better for me, 

 as she is the incubator. As I crawl on with the successive 

 classes I am astonished to find how similar the rules are about 

 the nuptial or " wedding dress " of all animals. The subject 

 has begun to interest me in an extraordinary degree ; but I 

 must try not to fall into my common error of being too 

 speculative. But a drunkard might as well say he would 

 drink a little and not too much ! My essay, as far as fishes, 

 batrachians and reptiles are concerned, will be in fact yours, 

 only written by me. With hearty thanks. 



Yours very sincerely, 



CH. DARWIN. 



[The following letter is of interest, as showing the exces- 

 sive care and pains which my father took in forming his 

 opinion on a difficult point :] 



C. Darwin to A. R. Wallace. 



Down, September 23 [undated]. 



MY DEAR WALLACE, I am very much obliged for all your 

 trouble in writing me your long letter, which I will keep by 



* In most of the Lophobranchii the male has a marsupial sack in which 

 the eggs are hatched, and in these species the male is slightly brighter col- 

 oured than the female. But in Solenostoma the female is the hatcher, and 

 is also the more brightly coloured. ' Descent of Man,' ii. 21. 



