Vol. XV. August, igo8. No. 



BIOLOGICAL BULLETIN 



THE SEGREGATION OF THE GERM-CELLS OF 

 PHRYNOSOMA CORNUTUM : PRE- 

 LIMINARY NOTE/ 



MAY M. JARVIS, 

 Tutor in Zoology, University of Texas. 



The changes that have been effected in the theories of germ- 

 cell origin since 1870 are characteristic of the advance of scientific 

 thought in general. Waldeyer's theory (1870) of their origin 

 from peritoneal cells was, in its very simplicity, so attractive that 

 it received universal recognition ; and since Nussbaum's opposing 

 theory (1880) that the germ-cells are to be observed in the late 

 cleavage stages of the egg, there has been continual controversy 

 over every new detail. The phenomenon of migration of the 

 germ-cells was observed in sponges long before Nussbaum ; Bal- 

 four's evidence (1878) indicates a migration from the mesentery 

 to the genital ridges, and Balfour admits the possibility of a 

 migration from the blastoderm ; Weismann proved conclusively 

 its occurrence in the hydroid polyps ; and yet modern embry- 

 ologists seem slow to admit that the primitive germ-cells in 

 vertebrates have the power of independent movement. 



Eigenmann (1891) was the first to give a detailed account of 

 the wanderings of the germ-cells in vertebrates ; he described the 

 migration from before backward in Cymatogaster {Micronietnis), 

 and in 1896, a dorso-median migration in this teleost. Hoff- 

 mann (1892) noted a probable migration from the connective 

 tissue between splanchnic mesoblast and entoblast to the ger- 

 minal epithelium, and Rabl (1896) gave a detailed description of 

 their very general distribution in selachians. It would seem that 



1 Contributions from the Zoological Laboratory of The University of Texas, No. 93. 



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