BOTANY. 375 



ers or leaves, we may consider that what formed them has been more di- 

 rectly submitted to the various forces of nature, which I take to be occasioned 

 by the removal of the outer covering, by which material influx is quickened, 

 and the solar attraction caused to produce mightier developments. Thus it 

 has appeared to me that leaves are produced by the expansion of single 

 atoms which are not enclosed by the outer covering, and that every variety of 

 floral form is the expansion of the same under various circumstances of ex- 

 tension and cleavage. Thus the form of leaves would be accounted for. If 

 they are the extension of atoms, it is clear that they would, at all events to 

 some extent, preserve their shape; and this would to a great extent explain 

 their strong axial resemblance. It is true that objections, on the score of 

 latitude, may be raised against this hypothesis, and much, if not all, that I 

 have said; but, as I have before set down, such speculations are not entirely 

 useless. 



THE GENETIC CIRCLE IN ORGANIC NATURE. 



The following is an abstract of a paper read before the British Associa- 

 tion, 1859, by Dr. G. Ogilvie: 



Parental derivation, he observed, was now generally allowed as the sole 

 origin of organic beings; and the subject of discussion among physiologists 

 was no longer the admissibility of spontaneous generation, but the nature 

 of the derivation, as the case may be, from a single parent or a pair. The 

 former mode of origin, by what has been termed "gemmation," or the 

 "budding process," plays a very conspicuous part in the propagation of 

 many of the lower species, and by its periodic recurrence in conjunction 

 with the other form of reproduction, gives rise to the singular phenomena 

 known as alternation of generations. All cases of alternation were not, 

 however, to be regarded as precisely parallel; and it was the object of the 

 present paper to point out certain -differences dependent on the period of 

 the life-history of a species in which the process of gemmation is interpo- 

 lated. Three stages were distinguished in the life-history the Protomor- 

 phic, or that prior to the first appearance of the organization most charac- 

 teristic of the species; the Orthomorphic, or that marked by such typical 

 organism ; and the Gamomorphic, or that of the development of the repro- 

 ductive organs. In each of these stages we may have a process of gemma- 

 tion interpolated. The results contrast, especially as it occurs in the first 

 and last. As examples of the former, the Trematode and Cystic Entozoa 

 were referred to in the animal kingdom, and the Mosses among plants, in 

 all of which certain provisional forms are interposed between the ovum and 

 the embryonic rudiment of the typical form. The Polypifera and Cestoidea 

 among animals on the other hand, and the Ferns among vegetables, furnish 

 illustrations of alternation dependent on gemmation, in the gamomorphic 

 stage, and arising from the reproductive organs acquiring the characters of 

 detached and often highly organized structures comparable to independent 

 animals or plants. The Hood-eyed Medusa3 become in this way much more 

 conspicuous organisms than the Polype stock, whose organs they really are. 

 The Cestoidea are remarkable as presenting instances of a double alterna- 

 tion, from a process of gemmation occurring both in the cystic or protomor- 

 phic, and in the TaenSoid or gamomorphic stages. The author concluded by 

 indicating a parallelism between the phenomena of alternation and ceri.-iin 

 points in the embryogeny of the higher animals, and in the maturation of 

 the reproductive organs. The formation of double monsters in the higher 



