160 METAMOKPHOSES OF MAN 



associate those of the Hydra, the plant-bugs, and the 

 biphorae, and if we add the results of recent dis- 

 coveries to those of older ones, we shall see that the 

 phenomena of multiplication, which at first seemed 

 exceedingly unlike each other, assume a sort of rela- 

 tionship, and form a somewhat natural group. This 

 relationship was first made known by a Danish 

 naturalist in a work which has been justly celebrated. 

 By the publication of his treatise on " The Alternation of 

 Generations,"* Steenstrup did good service for natural 

 science ; and although we do not share all his opinions, 

 and even occasionally take quite an opposite view to 

 those he has put forward, nevertheless we accord him 

 full praise for all that is valuable in his researches. 



We have already seen that Bernard de Jussieu was 

 the first who discovered the Hydra's eggs. His suc- 

 cessors, looking on this form of reproduction as useless 

 to an animal which was propagated both by buds 

 and by fission, regarded these ova as pimples which 

 resulted from some disease ; in fact held that the Hydra 

 possessed no organ comparable with an ovary. These 

 germs were secreted, so to speak, by the very walls 

 of the body. Upon some portion of the body, and 

 usually when buds have appeared, the skin is pushed 

 out in the form of a cupel : in this spot the elements 

 of the egg are gradually accumulated, and become 

 surrounded by a sort of shell or covering furnished 

 with bifid spines. The skin next bursts, and the 

 ovum thus expelled attaches itself to the nearest body. 



* "Ueber den Generationswechsel, oder Fortpflanzung und 

 Entwickelung durch abwechselende Generationen," 1842. This 

 work, to which we shall allude in the next chapter, was translated 

 into English for the Ray Society by Mr. George Busk, F.E.S. 



