A CASE OF FACULTATIVE PARTHENOGENESIS. 4! 



mosomes (case 2 A), the latter with the diploid number (2.5). 

 Spermatogenesis and fertilization are the same as in the bee 

 (Neuroterus according to Doncaster, '10). If parthenogenesis 

 results in female offspring, development occurs with the diploid 

 number, no reduction taking place in spite of two maturation 

 divisions (Nematus, Doncaster, '09, Rhodites, Schleip, '09). Oc- 

 casional males as in 2 A or 2Cb. 



2. Rotatoria. The relation of parthenogenesis to sex seems 

 to be exactly the same as it is in Hymenoptera. (Lauterborn, 

 '98, Shull, '10, Whitney, '09). Parthenogenetic eggs without 

 reduction give females, with reduction males, the latter if fer- 

 t'h'zed, females. We must suppose that the Spermatogenesis is 

 similar to that of the bee. 



3. Aphids. The well-known work of Morgan ('09) and von 

 Baehr ('09) shows them to fall into case B. 



4. PJiasmids. Their behavior is not yet clear, either experi- 

 mentally or cytologically. Probably they behave like some gall- 

 wasps with occasional males (see von Baehr, '07). 



5. Lepidoptera.The group of the Psychidae, which exhibits 

 regular parthenogenesis, is cytologically most interesting, as 

 will be shown in a paper by Dr. Seiler now in press. The results 

 seem to fit our conceptions. About the cases of facultative 

 parthenogenesis as described here we know only that both sexes 

 are produced and contain the diploid number of chromosomes. 

 We must suppose that we are concerned with case iCb or iCb 

 combined with iB or iCa. 



6. Ostracoda and Cladocem. Although these groups are greatly 

 favored by experimentalists, we know comparatively little 

 about their cytology (Woltereck, '98, Schleip, '09, Kuehn, '08). 

 It is possible that they belong to the same group as the Rotatoria, 

 but in Ostracoda parthenogenetic female-producing eggs undergo 

 no reduction division. The experimental results in sex-produc- 

 tion in this group make it seem possible, however, that we are 

 here concerned with something quite different. This possibility 

 will be discussed on another occasion. 



7. Artemia. The most recent writers on the subject (Artom, 

 'n, Fries, '09) agree that the parthenogenetic races develop 

 with the diploid number of chromosomes, the bisexual races in 



