170 REPROIUCTION. 



earlier the epoch at which we examine them. No two ani 

 mals can be more unlike than an adult Medusa (Fig. 31 

 and an adult Campanularia, (Fig. 143;) they even seem to 

 belong to different classes of the Animal Kingdom, the for- 

 mer being considered as an Acaleph, the latter as 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 larvae of certain 

 intestinal worms, though they belong to a different depart- 

 ment, 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 appear- 

 ance 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, bo- 

 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 

 appreciable by our senses ; the character by which they 

 subsequently differ so much being not yet developed To 



