36 LOUIS AGASSIZ. 



have introduced mathematics also, and he has 

 advanced a new hypothesis about comets and 

 their long tails. . . . Our chief botanical 

 occupation this summer is the careful obser- 

 vation of all our plants, even the commonest, 

 and the explanation of whatever is unusual 

 or enigmatical in their structure. We have 

 already cracked several such nuts, but many 

 remain to be opened. All such puzzling speci- 

 mens are spread on single sheets and set aside. 

 . . . But more of this when we are together 

 again. . . . Dr. Leuckart begs you to study 

 carefully the " Hebammen Unke;"^ to no- 

 tice whether the eggs are already fecundated 

 when they are in the earth, or whether they 

 copulate later in the water, or whether the 

 young are hatched on land, and what is their 

 tadpole condition, etc. All this is still un- 

 known. . . . 



AGASSIZ TO BRAUN. 



Orbe, June 10, 1827. 



. . . Last week I made a very pleasant 

 excursion. You will remember that I have 

 often spoken to you of Pastor Mellet at Vall- 

 orbe, who is much interested in the study of 

 the six-legged insects. He invited me to go 



1 Bombinator obstetricans referred to iu a former letter. 



