AMERICAN BEE JOURNAL. 



EDITED AND PUBLISHED BY W. F. CLARKE, CHICAGO, ILL. 

 AT TWO DOLLAES PER ANNUM, PAYABLE IN ADVANCE. 



Vol. VIII. 



MARCH, 1873. 



No. C J. 



[Translated for the Smithsonian Institution.] 



Alternate Generation and Parthenogenesis in 

 the Animal Kingdom. 



A LECTURE DELIVERED BEFORE THE VIENNA SOCIETY 

 FOR THE DIFFUSION OF SCIENTIFIC KNOWLEDGE, BY 

 DR. G. A KORNHUBER. 



Among the various questions whose scientific 

 explanation is the province of animal physiology, 

 none has perhaps excited the interest of the people, 

 as well as of scholars, to a higher degree than the 

 propagation of organisms. 



While in former times naturalists entertained the 

 most various opinions and hypotheses, or indulged 

 in the most chimerical speculations, modern science, 

 armed with more perfect knowledge and greatly 

 improved instruments, and more familiar with 

 methods of exact research, has gradually succeeded 

 in shedding some light on these mysterious processes. 



These processes in general consist in this, that 

 certain bodily constituents are from time to time 

 separated from individual beings, and are devel- 

 oped into others of the same species. If the action 

 of a second animal substance is necessary on such 

 separated germs, which then show the character- 

 istic structure of eggs, and are called ova, the pro- 

 cess is called sexual propagation or generation ; 

 but if the germ under favorable external circum- 

 stances may become a new being without such 

 action, this more simple though less general process 

 is called unsexual or agamic reproduction. 



To the latter belongs a series of phenomena to 

 which I have the honor of directing your attention 

 this evening; phenomena which have been accur- 

 ately studied and verified only within the last two 

 decades. A law has been established of the highest 

 importance, not only to zoology but to all natural 

 science, which has been named that of "Alternate 

 Generation and Parthenogenesis." 



It was the brilliant Danish naturalist Steenstrup 

 who, in the celebrated essay on "Alternate Genera- 

 tion," (Copenhagen, 1842,) first showed the way 

 that would lead to a satisfactory explanation of the 

 complicated phenomena attending the multiplica- 

 tion of the lower forms of animal life. 



By alternate generation, Steenstrup understood 

 the power of an animal of producing progeny dif- 

 fering 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 grand- 

 mother. Sometimes this return to the original 

 form occurs only in the third, fourth, or yet further 

 removed generations. The peculiarity of this phe- 

 nomenon not only consists in the alternation of 

 different progeny, but also in that of sexual and 

 sexless reproduction. One generation may consist 

 of sexually developed males and females, and beget 

 young from eggs, and the next may be sexless, and 

 may bring forth young by fission, by buds or germs. 

 These animals capable of agamic propagation were 

 called nurses by Steenstrup, because it is their 

 function to provide for the alimentation and devel- 

 opment of the sexual animals. The number of 

 sexless intermediate generations, as well as their 

 degree of development and organization, differs in 

 different species. They either possess provisory or 

 temporary organs, and are therefore larvae, or they 

 are fully developed individuals, and already show 

 the construction and mode of life of the sexual 

 animals. The sexless larvas of animals, such as 

 butterflies, which undergo simple metamorphosis, 

 are distinguished from our nurses by their inability 

 to multiply by agamic reproduction ; so that we 

 may, according to Leuckart, consider alternate 

 generation with nurses as a metamorphosis com- 

 bined with agamic reproduction. 



Alternate generation, very aptly called metagenesis 

 by R. Owen, was first observed in the salpae, a kind 

 of mollusks which are as remarkable for their form 

 as for their mode of life. They belong to the tuni- 

 cata, and are found in great numbers in the ocean, 

 the Mediterranean, and in all southern seas. They 

 swim about a little below the surface, and present 

 the appearance of oval or cylindrical bodies, clear 

 as crystal, moving about either isolated or united 

 in long chains, by taking in water and expelling it 

 again. 



Our German lyric poet, Chamisso, remarked, in 

 his voyage around the world, that the isolated 

 salpaj could not be members of a severed chain, 

 because they did not resemble the individuals of 

 the latter. He furthermore recognized that the 

 solitary salpae always contained a progeny resem- 

 bling the chain, while the individuals of the latter 

 contained a foetus formed exactly like the solitary 

 salpse. Chamisso published his interesting obser- 

 vations in 1819, at Berlin, in an essay entitled Be 

 animalibus quibusdam e classe vermium linnxana, Fasc. 



