XXVIII 



ARTIFICIAL PARTHENOGENESIS IN THE EGGS OF 



FROGS 



During the first years of his work and later the writer 

 vainly applied the chemical methods of artificial parthenogenesis 

 to the eggs of fishes and of frogs. The reason for this failure 

 may possibly lie in the relative impermeability of the walls of 

 these eggs for the chemicals used. The walls of the eggs of 

 Fundulus are, as long as they are normal, not only impermeable 

 for salts but also for water. It seemed desirable that a method 

 of artificial parthenogenesis for vertebrates should be found 

 since it is so much easier to raise the larvae of vertebrates than 

 of invertebrates. It is under the circumstances no surprise that 

 such a method was found almost accidentally. In 1907 Guyer 

 published a paper in which he reported that by injecting lymph 

 or blood into the unfertilized eggs of frogs he succeeded in 

 starting development and even in obtaining two tadpoles. 

 Considering the importance of these experiments and since 

 they seem to have been overlooked, the writer feels justified 

 in quoting part of Guyer's note: 



During three successive springs (1905-7) the writer has experi- 

 mented on unfertilized frog eggs by injecting them with blood or 

 lymph of either male or female frogs. In all some fifteen hundred 

 eggs have been so operated upon. Shortly before the time for laying, 

 the eggs were taken from the uterus with every precaution to prevent 

 contamination by sperm. Those nearest the cloacal opening were 

 always set aside as a control and in not a single instance did any of them 

 develop. The other eggs were pricked with a very fine-pointed capil- 

 lary tube which had previously been charged with lymph and cor- 

 puscles by dipping it into the lymph or the blood of another frog. 



In eggs so treated numerous instances of cell proliferation and 

 embryonic development have been observed, provided the eggs were 



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