36 RICHARD GOLDSCHMIDT. 



prolonged period. He states, furthermore, that the maturation- 

 divisions in these eggs are normal. However, a full report of 

 this work never appeared. Since that time many investigators 

 have tried to get parthenogenetic offspring from the gypsy-moth, 

 always in vain. I know that many of those who worked experi- 

 mentally with the gypsy-moth have tried it again and again, 

 without any success. We and some of our students have used 

 most of our odd material in females for this purpose during the 

 last seven years. The complete failure in every case made us, 

 as well as other observers, believe that the old reports must be 

 based on experimental errors. Nevertheless they seem to be 

 true, for I finally, in 1915, succeeded in getting a parthenogenetic 

 egg-batch. 



In this case the conditions of the experiment excluded the 

 possibility of error. I had isolated, for a selection experiment, 

 4 caterpillars, which were kept in a fruit-jar with a tightly 

 screwed tin cover. After pupation three pupae died from poly- 

 hedra disease. The fourth, a female, hatched. As the experi- 

 ment was spoiled I left this individual in the closed jar, intending 

 to kill it later. When I opened the jar after a few days the 

 female was busy laying a regular normal egg-sponge, which is 

 normally never done by unimpregnated females. From this 

 parthenogenetic egg-batch, containing certainly over 200 eggs, 

 22 caterpillars hatched in the spring 1916 and were bred with 

 special care. Three died in early stages and the sex could not 

 be ascertained. Three died before pupation. They were fe- 

 males. Three were killed between the third and fourth moult 

 for cytological study, and proved to be one female and two 

 males. The remaining thirteen hatched and were three females 

 and ten males, the total thus being seven females, twelve males 

 and three unknown. The three females were tried again for 

 parthenogenesis and one of them after ten days finally laid a 

 normal-looking egg-batch. There can, therefore, be no more 

 doubt that facultative parthenogenesis occasionally occurs in 

 the gypsy-moth and results in the production of both sexes. We 

 do not, however, know whether favorable external conditions or 

 some hereditary or not hereditary quality is responsible for the 

 occurrence. The parthenogenetic mother was, in our case, an 



