5 I THE PEOPLE ^ 97 



shell Dentalium appeared in the first volume of the Journal of E^cperimental 

 Zoology; Costello's paper on Nereis is in the one hundredth volume. Clearly, 

 Costello felt very proud to belong to such a tradition of cell lineage studies 

 begun by Wilson and Conklin so long before at the MBL. 



In fact, he insisted to me when I was a fresh graduate student in the 

 history of biology that I should study Nereis myself. But he did not want me 

 ordering eggs or worms from the supply room. Rather, it was essential to 

 take Costello's own net and his light and obtain special permission to go to 

 the MBL dock at night. There in early summer, shining the artificial light 

 into the water mimics the full moon and stimulates the beautiful and 

 complicated mating maneuvers. The male and female worms begin to 

 dance toward the light. They trace out intricate spiral patterns in the water, 

 becoming more and more frenetic with time. Eventually the moment comes 

 when the females release their eggs and the males release their sperm into 

 the water, which suddenly becomes very cloudy. The embryologist can 

 either grab the worms just before that point or collect some of this water 

 and run for the lab to start watching cell division. The realization that simple 

 observations are extremely difficult to make, and that it is very tedious to try 

 to reproduce the meticulous cell lineage work that was done with simple 

 equipment a century ago is instructive. The sense of following the same 

 fradition of research as Wilson, Conklin, Costello, and others is also inspir- 

 ing. Some recent returnees to cell lineage work have similarly felt the 

 pleasure of participating in such traditions. 



Geneticist Tracy Sonneborn epitomized the feeling cind the excitement 

 at the MBL when he wrote to his aunt and uncle. He wanted to thank them 

 for their generous twenty-first birthday present and to tell them what he had 

 done with the money. As a student at Johns Hopkins under Herbert 

 Spencer Jennings, Sonneborn had enrolled in a summer course at the 

 MBL. He wrote from Woods Hole in 1926: 



If you could only know the childish delight and wonder and amaze- 

 ment which I have been experiencing the last few nights, you would be 

 certain [that I will never grow up]. I just wrote to mother about it, but I'm 

 going to write it to you because I want to be sure you hear. 



I've been staying up over my microscope the last few nights watch- 

 ing a new living being formed! Can you believe that? Well, it's absolutely 

 so. I've collected certain marine animals whose mating reactions are 

 governed by the moon; at full moon and for the first quarter tliereafter 

 they spawn. It is a simple matter to collect them at night with a flashlight; 

 they are strongly attracted to the light, just like moths and swim right up 

 to you so that they can be scooped out and brought to the lab. When I 

 am ready, I allow them to mate. Right away, I take a drop of water 

 containing hundreds of eggs and thousands of sperm and put it under 

 the microscope. Then I can see the whole drama in all its details. 



