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On Parthenogenesis. 399 



Aet. XXXII. — On Parthenogenesis, 



The subject of parthenogenesis in canimals, and especially with 

 reference to the Aphides or common plant-lice, was discussed in 

 this Journal, earlj in 1854, bj Dr. W. L Burnett. Dr. Burnett 

 brought to the question the results of his own minute researches, 

 carried forward with the exactness and skill which are knowji to 

 bave characterized all his microscopic investigations. Since 

 then, the subject has been growing in interest, and under its new 

 name, parthenogenesis, it is taking more the aspect of a recog- 

 nized principle in the Sciences of Life. The word, as its deriva- 

 tion implies, signifies the production of young by the female sex 

 alone; and in the Aphides, generation follows generation, for a 

 dozen or more, without renewed intercourse with the other sex. 



Dr. Burnett appreciated the fact, that there were two modes of 

 generation well known in plants and animals, — one by true eggs, 

 the other by buds without eggs. The plant kingdom is known 

 to be full of both processes- ' The bud from a branch, developing 

 regularly its leaves, and capable as it often is of propagation 

 when separated as well as when united to the original stem, is one 

 Tariety of propagation by buds. The bud originating as a bulb 

 at the axils of the leaves and branches, which drops off, and on 

 finding soil, produces a new plant, is another variety of growth 

 hy buds. As each plant from such a bulb or bulbel will pro* 

 duce its crop of bulbels, propagation may be continued on, ap- 

 parently indefinitely, without the necessary intervention of true 

 flowers. 



The Animal Kingdom in its inferior departments of the Radi- 

 ates and Molluscs, exemplifies the same method of propagation. 

 The young polyp may grow from the side of the old, and be 

 persistent, like ordinary buds of plants, but become an independ- 

 ent individual if cut off*; or in other cases, it may drop off on 

 Teaching towards maturity and thus acquire independence and 

 so become the parent of a new zoophyte. 



Thus far, the two kingdoms have been long known to be alike 

 in reproduction. The bulbels of the plant are not like true seed 

 in structure, neither are the bulbels of the Campanularida^. 

 There is not the germinal Vesicle with its germinative spot. 

 The development is simply gemmation. The analogies between 

 plants and animals, it may be stated, go still farther : for as plants 

 produce leaf buds, and then flower buds in which sexual organs 

 ^nd seed are developed, so some Medusa (Tubularidae) bud out 

 ^olyps, to make the branching stems, and afterwards bud out 

 fedusse to develop sexual organs and ova : these Medusa? (as 

 occasionally happens with the flowers of plants) separating and 

 becoming free from the stalk that produced them. Moreover it 





