86 CLASSIFICATION OF MEDUSA. , 



argument drawn from analogy between the animal and vegetable kingdom, is as clearly and fully 

 expressed as in the sentences I am about to cite from the review itself. Indeed it was very 

 unlikely that a Lecturer on Botany* would allow such obvious analogies to escape him. 



The theory enunciated by Dr. Carpenter, and proposed to be substituted for that of 

 Steenstrup, has special reference to the Medusae and Polypes, and is stated in the following 

 passages : 



" The fertilized ovum of the medusa-parent is like the seed of the plant ; and the polype 

 that grows from it resembles the first leaf-bud into which the embryo expands. From this bud 

 are at first produced others, by the process of continuous growth, which are repetitions of 

 itself ; these in the plant usually remain connected with each other so as to form a compound 

 structure, and so they do also in the ordinary zoophyte ; but in the common hydra, and in 

 the hydraform medusa-larva, they become detached like the bulbels of the marchantia or lily. 

 But under certain conditions, a new and different set of buds, containing a sexual apparatus, 

 are produced ; these, too, become detached, and, by their inherent powers of movement, they 

 convey the germs of a new generation to a distance from the parent stock. The whole of these 

 phenomena appear to us to constitute but a single generation, instead of two, as represented 

 by Steenstrup. We are not in the habit of speaking of the leaf-buds and the flower-buds of a 

 plant as of two distinct generations ; nor, if our comparison be correct, have we any ground 

 for giving such a designation to the polypoid larva, and the medusa-imago, which are con- 

 tinuous developments from the same germ. Hence the whole doctrine of the ' alternation of 

 generations,' falls to the ground, so far as this individual case is concerned ; the phenomena 

 being simply those of metamorphosis or change of form, attending the evolution of successive 

 products from the same original germ. The metamorphosis is not really so great as that 

 which presents itself in the course of the development of any one of the higher organisms, 

 the several parts of which depart more widely from each other, and from the early embryonic 

 cell-cluster, than do the polype-buds and medusa-buds we have been describing. The chief 

 difference lies in the capacity of the latter to maintain a separate and independent existence ; 

 a capacity which is evidently connected with their low type of organization." (Review 

 cited, p. 23.) 



And again, in the recapitulation (at p. 29) — " The true Hydra, which may be regarded as 

 uniting the general form and structure of the polype with the locomotive powers and dis- 

 positions of the medusa, propagates in both the modes characteristic of the vegetable 

 kingdom ; namely, by gemmation, and by the production of ova. The buds are not destined 

 to remain in continuity with the parent, but are thrown off like the bulbels of certain plants ; 

 having previously acquired, however, the form of the parent. The ova also are developed 

 into polypes resembling the parent. The usual mode of propagation is here by bulbels ; the 

 ova being destined apparently to continue the race through the winter season, the cold of 

 which might be fatal to the parents. 



" In other cases, however, we find a greater specialization of characters ; the locomotive 

 and proper generative apparatus being especially developed in the Medusce ; whilst the true 

 polypoid condition presents its most complete evolution in the plant-like SertularidcB, yet 

 these two groups are not to be dissociated from one another ; for each of them, in one of its 



* Professor Steenstrup was Lecturer on Botany and Mineralogy in the Academy of Soroe. 



