CONSEQUENCES OF ALTERNATE REPRODUCTION. 139 



(Fig. 143) ; they even belong to different classes of the 

 Animal Kingdom, the former being an Acaleph, the latter a 

 Polyp. On the other hand, if we compare them when first 

 hatched from the egg, they appear so much alike that it is 

 with the greatest difficulty they can be distinguished. 

 They are then little Infusoria, without any very distinct 

 shape, and moving with the greatest freedom. The larvse of 

 certain intestinal worms, though they belong to a different 

 department, have nearly the same form, at one period of 

 their life. Farther still, this resemblance extends to plants. 

 The spores of certain sea-weeds have nearly the same 

 appearance as the young Polyp, or the young Medusa ; and 

 what is yet more remarkable, they are also furnished with 

 cilia, and move about in a similar manner. But this is only 

 a transient state. Like the young Campanularia and the 

 young Medusa, the spore of the sea-weed is free for only a 

 short time ; soon it becomes fixed, and from that moment 

 the resemblance ceases. 



360. Are we to conclude then, from this resemblance of 

 the different types of animals at the outset of life, that there 

 is no real difference between them ; or that the two King- 

 doms, the Animal and the Vegetable, actually blend be- 

 cause their germs are similar ? On the contrary, we 

 think nothing is better calculated to strengthen the idea of 

 the original separation of the various groups, as distinct and 

 independent types, than the study of their different phases. 

 In fact, a difference so wide as that between the adult 

 Medusa and the adult Campanularia must have existed even 

 in the young ; only it does not show itself in a manner to be 

 appreciable by our senses ; the character by which they sub- 

 sequently differ so much, being not yet developed. To 

 deny the reality of natural groups, because of these early 

 resemblances, would be to take the appearance for the 

 reality. It would be the same as saying that the frog and 



