146 K. MITSUKUEI, HOW MANY TIMES DOES 



number of deposits made in the farm for each day of the season shows 

 in the diagram for 1889 four distinct peaks. This can now be in- 

 terpreted as indicating that most individuals made in that year four 

 deposits of eggs. This interpretation is strengthened by the fact that 

 the days covered by these four peaks coincide ahnost exactly with the 

 dates of tha four deposits in the first of the tables given above. In 

 other years the third and fourth peaks overlap — a fact which has greatly 

 obscured the meaning of these diagrams. 



My present views in regard to this phase of the oviposition of 

 Trionyx may be stated as follows : — 



During certain warmer moiiths of tJie year (May, June, July, and 

 August"^) -when the temperature is luitJiin certain limits, successive 

 crops af eggs rapidly mature and are deposited as soon as they mature. 

 As a general thing, tliree or four deposits are thus made in the course of 

 one season — the difference in the number being mainly due to meteorolo- 

 gical conditions, but perhaps also to some extent to other circiunstances 

 such as the healthy or unhealthy condition of p)onds, the age of in- 

 dividuals, or the supply of food. 



My obsevations have all been made on individuals in captivity, but 

 some individuals have been in that condition for over twenty years and 

 the condiiions are so natural that I can not think wild individuals would 

 behave in a very much different manner. An abundant supply of food 

 may possibly enable those in captivity to make one deposit more than 

 wild ones but there is no evidence whatever in either direction. 



In this connection, the statement of L. Agassiz in regard to the 

 North American Testudinata is interesting. He says : " No one of our 

 Turtles makes more than a single nest."f As the northern part of the 

 United states is much severer in its climatic conditions than Japan, we 

 may suppose that there is in that region time enough for only one crop 



* The earliest date of egg-laying known to me is May 30 and the latest Aug. 13th. 

 t L. .'\gassiz : Contribution to the Nat. Hist, of the U. S. Vol. II. p. 497. 



