Jax. 1902.] BOTANICAL SOCIETY OF EDINBURGH 131 



have only been drawn to six divisions, giving sixty-four. 

 To exactly embrace the full significance of the discovery, 

 the drawing ought to include three further divisions, yield- 

 ing five hundred and twelve germ-cells at P.G.C. 



That is to say, to accurately represent the conditions in 

 embryo no. 454, for example, the diagram ought to be at 

 P.G-.C. eight times as wide as it is at present ! 



When I see in this diagram some of the results of 

 twelve years of work, the reader will perhaps pardon me, 

 if I linger to say something more concerning it and its 

 origin. Some parts of it will be familiar to every embryo- 

 logist, thanks to the work of Boveri, 0. Hertwig, and 

 others ; the other and unfamiliar portions are my own. 



Following out the full history of the diagram, I am 

 carried back more than twelve years. As long ago as 

 1888 my researches on larval strvictures in fishes 

 commenced. Their results in course of time carried 

 the investigator in the direction of the recognition of an 

 antithetic alternation of generations. Since that stand- 

 point was attained, no facts adverse to it have been 

 encountered. The doctrine has never been seriously 

 attacked : it has been simply ignored. It has not 

 as yet won many adherents : the truth never does 

 at first. For myself, I have been content to follow 

 out the inquiry, and from time to time, as oppor- 

 tunity offered, to glean a few more facts supporting 

 this theory of development. During part of this period a 

 watch has been kept for something equivalent to the 

 formation of spore-mother-cells in the higher plants or 

 Metaphyta, but in vain. Hitherto, as at length clearly 

 recognised, the search had not been made in the right 

 place. 



The investigator is often the creature of circumstances. 

 These in the present case brought about an investigation of 

 the early history of the germ-cells without associating with 

 this inquiry any ideas concerning spore-mother-cell-forma- 

 tion or alternation of generations. 



Only when the work was practically ready for publica- 

 tion, and when a proper survey of the results had been 

 obtained, by drawing them up in diagrammatic form, as 

 shown in the table, the full force of the discovery became 



