GENERATION. 



[ 288 J 



GEORGIA. 



4. Many animals and all plants are 

 capable of being multiplied by this vegetative 

 reproduction in their intermediate stages of 

 extra-uterine development, and in such cases 

 the reproduction, fissiparous, gemmiparous, 

 or other, assumes the character peculiar to 

 the class to which the intermediary form is 

 analogous {ex. gr. the polypiform reproduc- 

 tion of the AcalephfE, the confervoid growth 

 and multiplication of the proembryo of the 

 Mosses). The product of the vegetative 

 reproduction is either like or unlike the 

 body which produces it ; in the former case 

 the vegetative reproduction will be re- 

 peated, but in the latter case the product is 

 usually provided with sexual organs, and the 

 cycle of development is completed by the 

 reproduction of a fertilized ovum. In the 

 latter case we have what is called an alterna- 

 tion of generations. 



It will be evident that we here exclude 

 from consideration the metamorphoses 

 within the sphere of the individual shoot on 

 plants, that is, the metamorphosis of the 

 leaf, the morphological element of the higher 

 plant. It appears to vis that these are not to 

 be taken as parallels to the metamorphoses 

 of animals comprehended by Steenstrup 

 under the name of alternation of generations, 

 which would rather be found in the cases 

 where bulbs, bulbils, tubers, &c. appear in 

 the place of shoots, as the product of 

 branch-buds. The analogy would hold also 

 with the gemmce of the Mosses, &c., and with 

 the gonidia of the Thallophytes. Our space 

 does not admit of a more minute examina- 

 tion of the subject. Illustrations of the 

 phsenomena in vegetables will be found 

 under Ferns, Mosses, Confervoids, 

 Lichens, certain Fungi, e. g. Erysiphe, 

 Penicillium, &c. 



BiBL. Steenstrup, Alternation of Gene- 

 rations, Trans, hy Ray Soc. 1845; Owen, 

 Parthenogenesis and Ann. Nat. Hist. 1851. 

 ii. 59; Allen Thomson, Cycl. Anat. iv. 

 Supplem.; Huxley, Ann. Nat. Hist. 1851. 

 viii. p. 1., Brit, and For. Med. Rev. 1854. i. 

 204; A. Braun, Rejuvenescence in Nature, 

 Transl. by Bay Society, 1853. 



GENERATION, SPONTANEOUS; some- 

 times called equivocal generation, or epige- 

 nesis. 



The doctrine of spontaneous generation 

 may now be said to have become a matter of 

 history. We have noticed under Air (p. 20), 

 the experiment which negatived the idea 

 that microscopic plants and animals derive 

 their origin from the direct transformation 



of decaying animal and vegetable remains. 

 We have also there stated the modes by 

 which the lower forms of organic life, most 

 commonly found in decomposing infusions, 

 propagate with extraordinary rapidity. The 

 other two principal instances which were 

 supposed to favour the doctrine of sponta- 

 neous generation, were the production of 

 the Spermatozoa and of the Entozoa. 



It need scarcely be remarked that the Sper- 

 matozoa cannot be regarded as animals; they 

 are products of the metamorphosis of the con- 

 tents of cells (Spermatozoa, Sperm ato- 

 zoiDs); and the only ground for considering 

 them as animals was based upon their power 

 of motion, which we now know to be no ex- 

 clusive character of animality. The supposed 

 occurrence of particular species of Entozoa 

 within the bodies of other animals, not to be 

 found in any other situations, would natu- 

 rally appear to find a ready explanation in 

 the doctrine in question. Recent investiga- 

 tions have, however, proved that these sup- 

 posed species are larval or other forms of 

 true species of this Class, which do not 

 attain their perfect development on account 

 of their not existing in a suitable locality. 



See Generations, Alternation 



OF. 



BiBL. Schultz, Poggend. Annal. xli. 

 p. 184 ; Helmholtz, Journ. f. Prak. Chem. 

 xxxi. 429; Gross, Sieb. and Kollik. Zeitschr. 

 iii. p. 68 ; Reissek, Ber. d. Akad. z. Wien. 

 1851 ; Pineau, Ann. des Sc. nat., Zool. 1845. 

 1848. 



GEOPONUS. See Foraminifera. 



GEORGIA, Ehrh.— A 

 genus of Mniaceous Moss- 

 es, called from the four 

 teeth of the peristome, 

 Tetraphis and Tetradon- 

 tium, but these names are 

 of later date than Ehrhart's 

 (1780). G. Mnemosyne 

 presents, besides its male 

 and female inflorescence, 

 a peculiar form of terminal 

 leafy bud (fig. 282), which 

 produces stalked gemmae 

 in the interior. In the 

 figure numerous arche- 

 gonia are also shown. 



Georgia Browniana, 

 C. Mull. = Tetraphis 

 Browniana, Grev. 



G. Mnemosyne, Ehrh. Georgia Mnemosyne. 

 mi. -L- n  1 A shoot With two 



= letraphlS pellucida, terminal leafy buds. 



Hedw. Magn. 15 diameters. 



Fig. 282. 



