ZOOLOGY: H. E. JORDAN 
271 
THE HISTORY OF THE PRIMORDIAL GERM CELLS IN THE 
LOGGERHEAD TURTLE EMBRYO 
By H. E, Jordan 
DEPARTMENT OF ANATOMY. UNIVERSITY OF VIRGINIA 
Communicated by A. G. Mayer, January 20. 1917 
In view of the wide discrepancies in the pubHshed accounts of the 
germ-cell history in various vertebrates, it seems very desirable that 
the problem should be reinvestigated among a greater range of forms, 
and by additional workers. 
The present study represents an attempt to trace the complete early 
history of the genital cells in a peculiarly favorable form, and, in the 
light of this data, to correlate the mass of apparently discordant obser- 
vations recorded for other vertebrates. 
The material employed consists of embryos of the loggerhead tur- 
tle, Caretta (Thallassochelys) caretta, from the two- to the thirty- 
two day stage of incubation. Parallel series were prepared by the 
Flemming-iron-hem.atoxylin and the Helly-Giemsa technics. 
This material possesses the following combination of unusual advan- 
tages for such study: (1) it can be procured in great abundance; (2) the 
developmental process is relatively slow (the incubation period extends 
through fifty-six days), yielding thus a closely graded series of stages; 
and (3) the germ cells are abundant and at all stages sharply demarked, 
by size, shape, and nuclear and cytoplasmic characteristics, from the 
cells with which they seemed possibly to have been confused in some 
forms, especially the less differentiated yolk-laden entoderm cells, and 
certain blood granulocytes (eosinophiles) . 
I am indebted to the kindness of the Carnegie Institution of Wash- 
ington and to Dr. Alfred G. Mayer, Director of the Department of 
Marine Biology, for the opportunity of collecting this material on 
Loggerhead Key, Florida, during the summer of 1914. 
The fundamental controversy concerning the history of the germ 
cells in vertebrates centers about the question of their relationship to 
the so-called 'germinal epithelium' of the genital ridge. Waldeyer^ 
maintains that in the chick certain cells of the portion of the peri- 
toneal epitheHum covering the primitive gonad differentiate into germ 
cells. Nussbaum^ was the first to controvert this theory, claiming 
that the germ cells are early segregated (in trout, frog and chick em- 
bryos) from the soma cells and that they subsequently wander from 
originally widely scattered regions into the differentiating sexual glands. 
