350 EEPEODUCTION. 



trary, is produced in a different manner, as we have shown 

 in the preceding paragraphs ; as among the medusae, by trans- 

 verse division ; among the polyps and the salpse, by buds, &c. 



540. The subsequent generations are moreover not to 

 be regarded in the same light as those which first spring 

 directly from eggs. In fact, they are rather phases of de- 

 velopment than generations properly so called ; they are either 

 without sex, or females whose sex is imperfectly developed. 

 The nurses of the Distoma, the Medusa, and the Campamdaria, 

 are barren, and have none of the attributes of maternity, ex- 

 cept that of watching over the development of the species, 

 being themselves incapable of producing young. 



541. Another important result follows from the above 

 observations, namely, that the differences between animals 

 which are produced by alternate generation are less, the 

 earlier the epoch at which we examine them. No two 

 animals can be more unlike, than an adult Medusa (fig. 

 366, k}, and an adult Campanularia (fig. 367) ; they even 

 seem to belong to different classes of the animal king- 

 dom, 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 larvae of certain intestinal 

 worms, though they belong to a different department, have 

 nearly the same form, at one period of their life. Further 

 still, this resemblance extends to plants. The spores of cer- 

 tain sea-weeds have nearly the same appearance as the young 

 polyp, or the young Medusa ; and what is yet more remark- 

 able, 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 only for a short time ; it soon becomes fixed, 

 and from that moment the resemblance ceases. 



542. 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 because 

 their germs are similar ? On the contrary, we think nothing 

 is better calculated to strengthen the idea of the original sepa- 

 ration of the various groups, as distinct and independent 



