700 OCEANOGRAPHY 



behavior of Clemmys. When once it begins the process of egg-laying 

 it is never deterred from carrying it out, no matter how near or how 

 boldly one may approach. Whenever I watched a Clemmys working 

 away in the direct midsummer rays, with its carapace all dried up 

 and with its eyes alone moist, I could not help comparing it to a slave 

 of duty fulfilling his fate with tears in his eyes. What causes such 

 a difference of behavior in the two species? What is its significance? 

 What difference in the nervous system corresponds to it? 



The traces of a spot where the snapping- turtle has laid eggs are 

 (1) the two marks made by the forepaws holding on to the earth 

 during the whole operation, and (2) a disturbed place some distance 

 back of the line of the forepaws where the hole has been made. The 

 three marks are at the angles of a triangle. I have noticed a very 

 interesting fact in regard to these traces. When a young female is 

 depositing her first eggs, she is very clumsy, the hole being badly 

 made and the filling-in of it very imperfect, so that often a part of it 

 remains open. Old females are extremely neat in their doings, and 

 one can determine at once the age and size of the female by the 

 skill displayed and by the distance between the three marks of egg- 

 deposition. This shows that, although the elaborate actions neces- 

 sary in egg-laying must be, in the main, due to instinct, each indi- 

 vidual has to add its own experience to the inherited impulses, and 

 is able thus only to accomplish the desired end with perfection. 



In Hattori's farm a person goes around the "parents' pond" once 

 a day or so and covers up with wire baskets all the new deposits 

 made since the last visit. Each basket may be marked with the date 

 if necessary. This covering serves a twofold purpose, the obvious 

 one of marking the place, and in addition that of keeping other 

 females from digging in the same spot. When hundreds, or even 

 thousands, of these baskets are seen along the bank of a "parents' 

 pond," it is a sight to gladden the heart of an embryologist, to say 

 nothing of that of the proprietor. 



The hatching of the eggs takes, on an average, sixty days. The 

 time may be considerably shortened, or lengthened, according to 

 whether the summer is hot and the sun pours down its strong rays 

 day after day, or whether there is much rain and the heat not great. 

 It may become less than forty days or more than eighty days. 

 By the time the last deposits of eggs are made in the middle of 

 August, the early ones, which were laid in May or June, are ready 

 to hatch; and inasmuch as, if small tortoises that have just emerged 

 from the eggs are allowed to get into the " parents' pond," they 

 are devoured by their unnatural fathers and mothers, a special ar- 

 rangement has now to be put up to prevent this. The left side of the 

 plan in Fig. 2 is intended to show this arrangement. Long planks 

 about eight inches wide are put up lengthwise around the edge of 



