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ZOOLOGY: H. E. JORDAN 
4. A certain number of germ cells migrate out of the regular germ- 
cell route and go astray. Such 'strays' are especially numerous in the 
periaortic mesenchyma where they may become incorporated among 
the neuroblasts of the developing peripheral sympathetic ganglia. The 
majority of these strays probably degenerate in situ, but some may 
possibly persist to form, under the proper pathologic stimulus, a focus of 
neoplastic growth. An occasional cell is found also in the blood ves- 
sels of this region. Such may be carried by the blood stream to dis- 
tant regions and perhaps again enter the mesenchyma or degenerate 
within the vessels. 
5. The total number of primordial germ cells counted in a twelve- 
day embryo is 352, the number within the gonads being about equally 
divided between the two (118, left to 127 right). 
6. Occasional cells may divide by mitosis or undergo degeneration 
at any stage of their history or at any point of the route. Mitoses 
are relatively more numerous during earlier stages and among the en- 
todermal cells; degeneration is more general during the later stages 
and in the mesenchyma of the closed hind-gut. 
7. No germ cells were found contributing to the formation of the Wolf- 
fian duct. There is no evidence in this form in support of von Beren- 
berg-Gossler's claim, on the basis of his observations on the lizard 
embryo, that the so-called primordial germ cells represent simply a 
belated stage of mesoderm formation from entoderm. 
8. The germ cells do not differ from young somatic cells in the char- 
acter of their mitochondrial content. The mitochondria include granu- 
lar as well as beaded rod and filamentous forms. 
9. No transition stages between celomic epithehal cells and germ 
cells appear up to the thirty-second-day stage. From the sixteen-day 
stage on, when the nuclei of some of the germ cells within the gonads 
became coarsely granular and the reticulum stains more deeply, appar- 
ent transition stages occur between the larger of the mesenchymal 
cells and the smaller included subepithelial germ cells. But no secure 
histologic basis can here be found for separating the germ cells of the 
gonads into large ''primary genital cells" and smaller "secondary geni- 
tal cells" (Felix) or gonocytes (Dustin), derived by process of differentia- 
tion from the cells of the germinal (peritoneal) epithelium or the sub- 
jacent mesenchyma. The size variations among the germ cells of the 
gonads of the older stages are no greater than in the original cords of 
the area pellucida or in the subsequent early stages; and the cytologic 
similarity between the two dimensional grades of cells is much closer 
than between the larger mesenchymal cells and the smaller germ cells. 
10. The evidence derived from a study of the Caretta embryos is 
