Embryonic History of the Germ-Cells of the Loggerhead Turtle. 323 



The periaortic germ-cells migrated dorsally (perhaps only temporarily) 

 instead of laterally across the coelomic angle, some apparently finding 

 their way into blood-channels. The germ-cells within the gonads are 

 about equally divided between the mesothelium and the subjacent 

 mesenchyma. The mesothelium consists of only a single layer of 

 prismatic cells, greatly flattened where they overlie a germ-cell. 



Chart showing the distribution of the germ-cells in a 12-day embryo. 



The cells occur from the level of the open gut to that of the end of the closed hind-gut, from slides 11 to 16, 

 a distance of 3 mm. Slides 11 and 12, a distance of 0.8 mm., include the open portion of the hind-gut. 



OLDER EMBRYOS; FROM 13 TO 32 DAYS. 



The 13-day embryo is essentially like the one of 12 days (figs. 1, 2, 

 and 3, plate 6), except that relatively fewer germ-cells remain in the 

 gut and more are found within the gonads. In the 16-day embryo 

 (11 mm. in length, from cephalic to caudal bend) the germ-cells have 

 practically all migrated into the gonads, where they come to rest, 

 both among the mesothelial cells and in the subjacent mesenchyma. 

 In the stouter mid-portion of the genital ridge (future gonad), where 



