ALTERNATE GENERATION AND PARTHENOGENESIS IN THE ANIMAL KINGDOM. 



Lecture delivered before the Vienna Society for the Dili'usion of Scieutilic Knowledge, 



by Dr. G. A. Koi:miuueu. 



'Xranslateil for tlie Smithsonian Institution. 



AmoDg" the variou.s questions whose scientific explanation is the 

 province of animal i>hjsiology, none has perhaps excited the interest 

 of the people, as well as of scholars, to a higher degree than the propa- 

 ga-tion of organisms. 



While in former times naturalists entertained the most various opin- 

 ions and hypotheses, or indulged in the most chimerical speculations, 

 modern science, armed ^Yith more perfect knowledge and greatly im- 

 proved instruments, and more familiar with methods of exact research, 

 has gradually succeeded in shedding some light on these mysterious 

 I)rocesses. 



These processes in general consist in this, that certain bodily constitu- 

 ents are from time to time separated from individual beings, and are 

 developed into others of the same species. If the action of a second 

 animal substance is necessary on such separated germs, which then 

 show the characteristic structure of eggs, and are called ova, tbe process 

 is called sexual propagation or generation; but if the germ under favor- 

 able external circum.stances may become a new being without such 

 action, this more simple though less general process is called unsex- 

 ual or agamic reproduction. 



To the latter belongs a series of phenomena toAvhich I have the honor 

 of directing your attention this evening ; phenomena which have been 

 accurately studied and verified only within the last two decades. A 

 law has been established of the highest importance, not only to zoology 

 but to hll natural science, which has been named that of '■'■ Alternate 

 Generation and Parthenogenesis P 



It was the brilliant Danish naturalist Steenstrup who, in the cele- 

 brated essay on "Alternate Generation," (Copenhagen, 1842,) first showed 

 the way that would lead to a satisfactory explanation of the complicated 

 phenomena attending the multii)lication of the lower forms of animal 

 life. 



By alternate generation, Steenstrup understood the power of an animal 

 of producing progeny dilfering from the mother, but itself capable of pro- 

 ducing young, which again return to the form and character of the first 

 parent; so that the daughter would not resemble the mother, but the 

 grandmother. Sometimes this return to the original form occurs only 



