. GERM-CELLS OF PHRYNOSOMA CORNUTUM. 1 25 



two indubitable germ-cells in the cavity of the yolk-stalk, and of 

 a third half imbedded in the entoblast and half projecting into 

 the same cavity, lends further support to the theory. However, 

 it will require an exact enumeration of the blastodermic and em- 

 bryonic germ-cells of many embryos at various stages, as well 

 as work along other lines, to determine the question in Pliryiw- 

 sonia. The possibility that these might be transitional forms be- 

 tween somatic and germ-cells is precluded, it seems to me, by 

 the fact that they are not found in what I have termed the path 

 of normal migration of the germ-cells, and especially by their 

 non-appearance in the germinal anlagen. 



Summary. 

 . I. The germ-cells appear first in the entoblast of the vascular 

 area of the blastoderm. They lie cephalad, caudad, and laterad 

 to the embryo. 



2. The germ-cells migrate in the entoblast of the blastoderm, 

 yolk-stalk, and intestine, and the sclerotome of the mesentery, 

 to J:he germinal anlagen. Very many leave this path and come 

 to lie in various regions of the embryo. 



3. Some of these abnormally placed germ-cells probably 

 degenerate. 



BIBLIOGRAPHY. 

 (Papers marked by an asterisk seen only in review.) 

 Allen, B. M. 



'06 The Origin of the Sex-cells of Chrysemys. Anat. Anz., Bd. XXIX. 

 '07 An Important Period in the History of the Sex-cells of Rana Pipiens. Ibid., 

 Bd. 31. 



Balfour, F, M. 



'78 On the Development of Elasmobranch Fishes ; reprinted in The Works of 



F. M. Balfour, Vol. I., pp. 345-354; London, 18S5. 

 Beard, J. 



'02a The Germ-cells of Pristiurus. Anat. Anz., Bd. 21. 



'02b The Germ-cells. Part I. Raja Batis. Zool. Jahrb., Anat. Abteil., Bd. 16. 



'04 The Germ-cells. Parti. Raja Batis. [Reprint of the preceding.] Journ. 



Anat. Physiol., Vol. 38. 



Bohi, U. 



'04 Beitrage zur Entwickelungsgeschichte der Leibeshohle und der Genitalanlage 

 bei den Salmoniden. Morphol. Jahrb., Bd. 32. 



*Bouin, P. 



'00 Histogenese de la glande genitale femelle chez Rana temporaria. Arch. 

 Biol., T. 17. 



