34 THE FACE OF THE FIELDS 



from the laboratory in Cambridge to some pond 

 when the turtles were laying, and back to the 

 laboratory within the limited time. And this, in 

 the days of Darius Green, might have called for 

 nice and discriminating work — as it did. 



Agassiz had been engaged for a long time upon 

 his " Contributions." He had brought the great 

 work nearly to a finish. It was, indeed, finished 

 but for one small yet very important bit of ob- 

 servation : he had carried the turtle egg through 

 every stage of its development with the single 

 exception of one — the very earliest — that stage 

 of first cleavages, when the cell begins to seg- 

 ment, immediately upon its being laid. That be- 

 ginning stage had brought the " Contributions " 

 to a halt. To get eggs that were fresh enough 

 to show the incubation at this period had been 

 impossible. 



There were several ways that Agassiz might 

 have proceeded : he might have got a leave of 

 absence for the spring term, taken his laboratory 

 to some pond inhabited by turtles, and there 

 camped until he should catch the reptile digging 

 out her nest. But there were difficulties in all of 

 that — as those who are college professors and 



