130 PHARMACEUTICAL BACTERIOLOGY 



stage at the time the hanging drop was prepared simply grow to maturity, 

 without actual numerical increase. There are however indications that 

 there is also actual increase by septation or by extension from the cell 

 plasm. 



That the fusion of gametes is intimately bound up with the activities 

 and evolutional development of the somatic cells, is indicated by the fact 

 that only those gametes which are derived from very closely related organ- 

 isms, will combine sexually. While it is quite evident that gametic repro- 

 duction is the product of environmental influences which have been at 

 work for ages, the why and wherefore of such reproduction is not clear. 

 To state that certain proteid stimulins or perhaps enzymatic bodies, 

 such as fertilizin, spermin, etc., are concerned in sex fusion and in sex 

 differentiation, does not materially clear the situation, unless we can explain 

 how and why these substances produce the effects ascribed to them. 

 Sex evolution still is and for some time to come will continue much 

 of a mystery. 



We may assume that it is an estabUshed fact that the somatic cell 

 preceded the germatic cell and that formed and living cell inclusions, such 

 as the chromoplasteds, chloroplastids, amyloplastids, leucoplastids, chro- 

 mosomes, directive spheres, chondriosomes, mitochondria, etc., have 

 their origin (phylogenetically as well as ontogenetically) in the cell plasm, 

 probably derived from fusing and septating plasmic granula and from 

 other as yet unrecognized ultimate plasmic elements. We are therefore 

 also justified in assuming that the essentials of cell growth and of reproduc- 

 tion reside in the plasm of the somatic cell and that mitosis which for several 

 decades has been looked upon as the dominant and all-important cell 

 activity, is of secondary significance. 



We have indicated the genetic relationship of somatic and germatic 

 cells, of single-celled and many-celled organisms, of cells and of cell contents, 

 of cell plasm and of chromosomes. It is believed that the observations of 

 sphaerocytes is further conclusive evidence that the cell plasm is the source 

 of all living inclusions and that the plasm of the somatic cell of higher organ- 

 isms may under certain conditions, produce not only a single cell but also 

 an indefinite number of secondary cells. This is evident from the study 

 of plant sphaerocytes. 



The sphaerocytes of plants are living structures derived from the cell 

 plasm, possessing the characteristics of the cells from which they are 

 derived. They occur largely extracellular, that is, outside of the mother 

 cell from which they originated, although in some fruits, as the grape and 

 the tomato, many are found within the cell. In the squash they appear 

 to be very largely if not wholly intra-cellular. In size they are extremely 

 variable, ranging from the limits of microscopic vision to over 100 microns 



