8 PREFACE 



figures which were described are really those of 

 cell-division or are merely some accidental dis- 

 tortion. It is difficult to discuss the pros and 

 cons of this point, because it is one about which 

 we are absolutely certain. Any one who has 

 seen the number of figures in all their phases 

 which we have seen cannot possibly dispute them; 

 and several persons have agreed that they are cell- 

 division. 1 Unfortunately, as I have said before, 

 one cannot always induce the division-figures 

 to order in such a manner that they resemble 

 the well-known aspects pictured so frequently in 

 text-books. There are many factors to be taken 

 into consideration, such as the temperature, the 

 consistency of the jellies, the vitality of the cells, 

 the alkalinity, the degree of putrescence of 

 extracts, and lastly the attitude which the cells 

 may happen to present to the observer, over which 

 we have no control whatever. Owing to scepticism 

 people will only come with reluctance to see the 

 experiments, and when they do arrive they fre- 

 quently expect us to command living cells to 

 undergo typically on every occasion the most 

 complex physiological function of reproduction 

 in the few moments which the visitors can spare 

 us. In work of this nature it is necessary to 

 spend many hours of careful observation, making 

 control experiments and searching through many 

 films. A cursory examination often leads to dis- 

 appointment. If a fairly typical specimen happens 

 to appear before the objective, however, many 

 people become convinced, although their ardour 

 is sometimes damped when they realise that the 



1 See letter in The British Medical Journal of January llth, 1911, 



