CULTIVATION OF MARINE ANIMALS IN JAPAN 697 



All the ponds, whether large or small, are constructed very much 

 on the same plan. They are limited on their four sides by plank 

 walls, the top of which may either be on the level of the ground 

 (see the right side of the section, Fig. 2), or may be more than a foot 

 above the ground when two ponds are contiguous (the left side, Fig. 2). 

 In either case the plank wall has a cross-plank of some width at 

 right angles to it on its top, and is also buried some inches in the 

 ground. The former arrangement is, of course, to prevent the tor- 

 toises from climbing over the wall, and the latter to prevent them 

 from digging holes in the ground and making their escape in that 



WVER 



FIG. 1. Plan of a turtle-farm 



way, while at the same time it serves to exclude the moles. On the 

 inner side of the plank wall there is more or less of a level space, 

 and then a downward incline of three or four feet. At the foot of 

 this incline and directly around the water's edge there is another 

 level space which enables people to walk around the pond. From the 

 edge of the water the bottom of the pond deepens rather rapidly 

 for a space of some three feet, and there reaches the general level of 

 the bottom, which is about two feet below the level of the water. 

 The greatest depth of a pond is about three feet and is always 

 toward the water-gate by which the pond communicates with the 

 canals. The bottom is of soft, dark mud, several inches thick, into 

 which the tortoises are able to retire to pass the winter. 



On a turtle-farm one or more of the ponds is always reserved for 

 large breeding individuals, or "parents," as they are called. The 

 just-hatched young or the first-year ones must have ponds of their 

 own, as must also the second-year ones; those of the third, fourth, 

 and fifth years may be more or less mixed. 



In order to give a connected account of the raising of tortoises, we 



