90 ZOOPHYTES. 



87. We pursue the subject by looking more minutely into the 

 elements engaged in the process of budding, to ascertain how the 

 principles drawn from the visible bud or polyp bear upon the internal 

 structure of the same. Plants afford us examples that illustrate the 

 facts in both kingdoms of nature. Growth, in its simplest condition 

 in plants, takes place by the budding of minute cellules, each in suc- 

 cession from a preceding ; and although vascular tissue and woody 

 fibre are added to the higher species, to give strength, yet, in all 



the interrupted surface of other Cyathophyllidse (§ 62), a similar effect appears to be 

 indicated, but dependent probably upon the developement of ovules rather than buds, 

 (and the preceding case may possibly be the same), the narrowing of the polyp being 

 consequent, as Ehrenberg suggests, on reproduction. This e.xhaustion is a well-known 

 fact in the animal kingdom ; the peculiarity in the case in question, is only in the mode 

 of e.\hibiting it, and the e.xtent to which it is carried. There is an analogy in the polyps 

 of certain zoophytes, dropping off and reappearing at intervals (§ 18), to the fall of the 

 flowers and leaves of a plant. Moreover, some species (Sertularidae) lose, from age, 

 their lower branches like vegetation, the trunk or stem, as in the vegetable kingdom, still 

 remaining alive. Buds often spring from a wound in a plant in greater numbers than 

 elsewhere ; and the Hydra affords an example of the same fact among polyps. 



The growth of palms has some resemblance to increase, among zoophytes, from a 

 terminal cluster; while budding from a parent-polyp, and the consequent lateral branch- 

 ing, produces forms more like those of our common trees. In the former, the buds pro- 

 ceed from the summit alone, and produce a lengthening cylinder, whose size depends on 

 the size of the cluster ; and, as the polyps lose the power of budding, they are turned 

 out from the summit cluster to join those of the lateral surface, just like the bases of the 

 falling leaves in the palm. This mode of increase, is still more like that in the Lyco- 

 podium ; for, in this genus, there is no internal growth, as thei'e is in the palms : it is 

 simply acrogenous, like the elongating coral stem. 



The explanate corals appear to be represented in the incrusting or foliaceous lichen, 

 and the massive hemispheres and globes in the globular Cacti ; and not only in external 

 form, but in actual constitution, for the Cactus consists of an aggregation of plant-indi- 

 viduals, as the Astrrea is composed of individual polyps united. 



Farther, we state that the modes of reproduction are as varied in the zoophyte as in 

 the plant. As we may obtain a perfect plant from a section, which includes, with a 

 leaf, its budding axil, so we may cut up a polyp, and, almost to the same extent, form 

 perfect individuals from sections : and, as the leaf will sometimes grow without the axil, 

 so in the rare instance of the Hydra, the tentacle alone is said to develope a complete 

 individual. 



Moreover, the mode of aeration, in many species, by the general surface, instead of 

 by special organs, affords another striking analogy to the vegetable kingdom. 



produced at apex, to form the stalk of the next season, and so on. In this manner, tlie rhizoma slowly 

 moves onward, from year to year, the scars marking tlie annual growth, and the more ancient portions 

 gradually decaying, as new parts are formed at the other extremity^ 



