FURTHER OBSERVATIONS ON THE PRODUCTION OF 

 PA RTHENO GENETIC FROGS. 



By JACQUES LOEB. 

 {From the Laboratories of The Rockefeller Institute for Medical Research) 



(Received for publication, January 19, 1921.) 



The writer has repeatedly pubhshed^ short reports on the produc- 

 tion of frogs from unfertilized eggs by Bataillon's method of punctur- 

 ing the membrane of the egg with a fine needle. The writer has 

 succeeded in raising over twenty of these parthenogenetic frogs to 

 an advanced and some to an adult stage. Two such specimens 

 (leopard frogs) are represented in Fig. 1, together with a scale giving 

 their size. They were at the time of death 13 and 14 months old 

 respectively, and the death of these, as of the other specimens, was 

 due to intestinal infection. The parthenogenetic frogs were appar- 

 ently normal in every respect. 



The second point of interest is the fact that both sexes occur among 

 the parthenogenetic frogs. Three females were obtained among over 

 twenty males, yet the preponderance of males may have been simply 

 an accident. Fig. 2 gives a macroscopic photograph of ovaries and 

 kidneys of one parthenogenetic female, and Fig. 3 a microphotograph 

 of a section through the ovary. The fact that both sexes occur 

 suggests that in the frog the female may be heterozygous for sex. 



It was ascertained that the male parthenogenetic frogs and tadpoles 

 possess a diploid and not a haplcid number of chromosomes. The 

 writer had the good fortune of obtaining the expert advice of Professor 

 Richard Goldschmidt,^ and later of Doctor Parmenter,-'' on this prob- 

 lem. Both authors found unquestionably a diploid number of chromo- 

 somes in the males. Parmenter was able to count definitely twenty- 



^Loeb, J., and Bancroft, F. W., /. Exp. ZooL, 1913, xiv, 275; 1913, xv, 379. 

 Loeb, J., Proc. Nat. Acad. Sc, 1916, ii, 313; 1918, iv, 60; The organism as a whole, 

 from a physicochemical viewpoint. New York, 1916. 



2 Goldschmidt, R., Arch. Zellforsch., 1920, xv, 283. 



3 Parmenter, C. L., J. Gen. Physiol. 1919-20, ii. 205 



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