Comparison of animal and vegetable repro duction.—In concluding this rapid it may not be out of place to introduce here a few remarks upon the analogies existing be tween animal and vegetable reproduction.
The seed of plants is generally regarded as corresponding to the egg of animals. The seed and egg correspond in being both the residence of the germ or living part from which the new organized body springs, and also in both containing a certain quantity of matter destined for the temporary nourishment of the growing embryo; but the germ is in a different state in the seed and egg ; for while in the egg none of the parts of the new being are visible at the time of its separation from the parent, the rudiments of the embryo are fre quently to be found,small but simulating in some degree the plant, in the germ of the seed when it is perfected, and before the commencement of germination. The circumstances favourable to evolution give rise to the development of the embryo in both, but in the animal the influence of the male conferring fecundity on the egg makes no perceptible alteration in the germ, while in the plant no part of the seed, neither cotyledon nor germ, is formed unless fecundation by the pollen of the male takes place; and the seed is not separated from the ovary or place of its production until the rudimentary parts of the embryo are already sketched out.
We have examples of non-sexual repro duction of plants among the Cryptogamia, in which the new plant springs from sporules or granules endowed with the independent vital properties of the seed.
The greater number of monocotyledonous and dicotyledonous plants may be regarded as hermaphrodite, as both the seeds and pollen are formed on the same individual, while in others the position of the sexual organs on distinct individuals corresponds with the more common arrangement in the animal king dom.* In different tribes of plants we also observe examples of occasional propagation in a man ner different from the more common one by seeds or sporules. Thus the buds and branches, which are the means of their ordinary growth and increase, may,when removed, be capable of independent existence and give rise to distinct plants, or even when still on the parent stock may take root and grow anew. Some buds separate naturally and are evolved in the man ner of seeds when placed in favourable circum stances; and in a third class of instances sepa rated buds are preserved in the collections of nutrient matter constituting the tuberous and bulbous roots by which many plants are pro pagated.
To complete the enumeration of the points of analogy between animal and vegetable re production, it may be stated that there is the same reason for believing in the spontaneous generation of some of the Cryptogamic plants as in that of Infusorial animals.
The following table is intended to exhibit a synoptical view of the various forms of the reproductive process occurring in different classes of animals.