THE AMEBIC A 



PARTHENOGENESIS AND SEXUAL REPRODUCTION IN 

 ROTIFERS. EXPERIMENTAL RESEARCH UPON 

 BRACHIONUS PAL A 1 



In a recent number of Bios Miss Lina Moro has presented some 

 interesting and suggestive results from experiments upon the 

 rotifer, Brachionus pala. She has subjected the parthenogenetic 

 females to various chemicals, to changes in nutrition, and to 

 changes in temperature. 



In using PeCl 3 solutions she has been able to produce male- 

 producing females in small numbers while in control experiments 

 in which no FeCl 3 was used no male-producing females were 

 produced. Many dilutions of FeCl 3 were used but M/12,000 

 seemed to be the optimum dilution. This was added to the cul- 

 ture water of hay infusion in which the rotifers were living. 

 Although the number of the experiments were rather small and 

 the percentage of male-producing females obtained was not 

 higher than 12 per cent., nevertheless they indicate the possi- 

 bility of a specific chemical being able to induce the production 

 of male-producing females. 



Not only did FeCl 3 cause male-producing females to appear 

 but it also caused the mothers to form the eggs much faster in 

 their bodies and to extrude them to the outside much faster than 

 those in the controls. Usually while a female in the control was 

 producing one egg a female in the FeCl 3 would produce four 

 eggs. This rapid formation and production of eggs after it was 

 once started continued through many subsequent generations 

 during the three months in which the experiments were carried 

 on. It might be considered that this new characteristic induced 

 by a chemical was a case of the formation of a new character 

 which, after it was once formed, was inherited by the descendants. 



It was also determined that the influence of the FeCl 3 acted 

 upon the egg while it was yet inside the mother and caused it to 

 develop into a male-producing female. After the egg was laid its 

 development could not be altered from a female-producing 

 female to a male-producing female by the use of FeCl 3 . 



A dilution of HgCl 2 (Jf/1,200,000,000) was also effective in 

 causing male-producing females to appear but a smaller number 

 of offspring were produced than in the FeCl 3 . The percentage 



i"Partenogenesi e Anfigonia nei Botiferi. Eecerche sperimentali sul 

 Brachxonus pala," by Lina Moro, Bios, Vol. 2, Fasc. 3, pp. 219-264, 1915. 



