124 PHARMACEUTICAL BACTERIOLOGY 



will show living cell elements which may be studied for many hours and 

 even days, and some of the plastids, chromophores and nuclei, will not 

 only remain alive for weeks when suspended in the hanging drop but 

 will also increase in size and in rarer instances will multiply by septation. 



We have from the first recognized and admitted the transmissibility 

 of the parental characteristics via the male and female germ cells, and such 

 hereditary transmission is undeniable. In order to explain the phyloge- 

 netic and ontogenetic relationship of the somatic cells and the germatic 

 cells, we must survey our present conception of the origin of the gametes 

 or the sexual reproductive cells. 



]We may assume that the original living structures or organisms con- 

 sisted of individualized bits of more or less complexly differentiated 

 plasmic substances and we may also assume that these plasmic units were 

 biologically somatic or trophic in character rather than germatic or re- 

 productive. We can readily comprehend why in the very nature of things 

 these living bits of plasm were self limited as to size and also as to duration 

 of existence, in all probability largely due to the limitations of available 

 food materials in the immediate vicinity of the originally motionless 

 plasmic units. 



The essential of reproduction is the detaching of a single cell or a group 

 of cells from the parent cell or parent body, capable of continued existence, 

 and growth. Three types of reproduction are generally recognized, vege- 

 tative reproduction, spore reproduction and sexual or gametic reproduc- 

 tion. In the lower plants and animals all three methods may be observed. 

 In the alga Ulothrix, for example, a portion of the vegetative filament 

 may become detached and such detached cell or group of cells will continue 

 growth and septation and finally develop into a new mature filament. As 

 the conditions for the purely vegetative method of reproduction became 

 more and more unfavorable, the contents of certain specialized cells of the 

 filament were formed into spores which possess the unusual quality of 

 being able to tide over an unfavorable period. In time even the spore 

 was no longer sufficient to enable the organism to survive the changing 

 environmental conditions and the gametic method was developed. There 

 certainly can be no doubt as to the priority of the vegetative method of 

 reproduction as represented by the simpler forms of cell septation and by 

 budding and the renewed growth of detached cell groups. In sexual re- 

 production we have the union or fusion of the chromosomes and perhaps 

 other essential elements of two different cells (male and female gametes) 

 of the same species. Since the somatic or vegetative cell and the vegeta- 

 tive methods of reproduction preceded the gametes and the sexual method 

 of reproduction, we must assume that gametes are somatic in origin, both 

 phylogenetically and ontogenetically. 



