AND THE LOWER ANIMALS. 241 



From this point of view we can at once understand 

 now it is that agamic reproduction cannot be indefi- 

 nite. Growth in every animal has its limits pre- 

 arranged. If, then, gemmation be a form of growth, it, 

 too, must have its limits ; therefore it cannot suffice 

 for the perpetuation of the species. Hence the inter- 

 vention of another mode of generation, by which the 

 continuance of the race becomes insured. As soon as 

 the process of gemmation ceases, the ovum exhibits 

 itself as the fundamental element; consequently, 

 even these animals most decidedly gemmiparous and 

 fissiparous — must, after a certain period, reproduce 

 themselves by ova. 



Once formed, the bud proceeds with its develop- 

 ment in the same manner as any other germ, and in 

 obedience to the same laws by which the ova of a 

 bitch, a hen, and a teredo are converted respectively 

 into a mammal, a bird, and a mollusk. From this, we 

 should expect to find, in its case, all those phenomena 

 which we treated of in our earlier chapters. Whether 

 the bud remains fixed, as in the Hydra, till the time 

 comes when it will have only to increase in size, or 

 detaches itself in the condition of an almost unorga- 

 nized mass, and falls into some special cavity, where 

 it undergoes its subsequent changes, as in the Aphides, 

 or is borne away to a distance, as in Synhydra, it 

 nevertheless undergoes a series of transformations and 

 metamorphoses similar to those we have described, 

 and it is only under the influence of the vital force 

 that it assumes its definitive form and proportions. 



These considerations lead us to believe that the 

 course which, in association with Dr. Carpenter, we 

 have struck out, is really the correct one. Without 



