34 



we should not, by that definition, have penetrated one step 

 into the mystery of the development by the gemmiparous 

 hydra of an offspring, without the preliminary act of im- 

 pregnation in its own person. 



Again : the simple hydra, which by gemmation produces 

 the hypothetical higher form of oviparous hydra, may be 

 designated a e larva/ as containing potentially, and con- 

 cealing, as it were by a mask, such higher form of animal. 

 Or, by another figure of speech, the simple gemmiparous 

 hydra may be called a e wet-nurse/ in the character of 

 carrying or contributing sustenance to a young indivi- 

 dual of a higher grade than itself. But neither of these 

 metaphors would convey to us an idea of the organic con- 

 ditions essential to the development by the larval or nursing 

 hydra of a bud producing another individual : they would 

 prove, I opine, to every thinking mind, very unsatisfactory 

 substitutes for such knowledge. 



The terms Generationswechsel, e alternate generation/ 

 and Amme, e wet-nurse/ have been, however, proposed by 

 Dr. J. J. Sm. Steenstrup, a learned and ingenious Danish 

 Professor of botany, in explanation of the " natural phae- 

 nomena of an animal producing an offspring, which at no 

 time resembles its parent, but which itself brings forth a 

 progeny that returns in its form and nature to the parent " 

 and these phaenomena, he writes, were "till now inexpli- 

 cable n (p. 1), meaning until the publication of his work 

 " Ueber den Generationswechsel," which has been trans- 

 lated by the * Ray Society ' with the title " On the Alter- 

 nation of Generations, or the Propagation and Develop- 

 ment of Animals through Alternate Generations, a peculiar 

 form of fostering the young in the lower classes of animals/^ 

 8vo, 1845*. 



I have carefully studied this work in the hope of ob- 

 taining some further insight into the mystery of Parthe- 

 nogenesis, or procreation by an animal without sexual 

 * This is the edition cited in the present discourse. 



