132 THE COTTON PLANT IN EGYPT chap. 



plexities presented by the other crosses, but it is as 

 complex in its own way as the Upland x Egyptian 

 series. It seems to be quite probable that this cross was 

 one between the old Peruvian and Sea Island stocks, and 

 was hence not very much more intimate than the Upland x 

 jEgypto-Peruvian crosses. 



The author can only reiterate his conviction that all 

 these hybrids are subject to Mendel's Law of segregation ; 

 often obscurely — on account of defective methods — 

 but none the less certainly. The evidence available can 

 all be interpreted in Mendelian terms, and it is very 

 significant that most of it should appear at first glance to 

 be completely dissociated from the classical ratios. 

 Mendelian students of heredity have confined themselves 

 to the more definable characters, such as colour, partly 

 because statistical characters take up an excessive amount of 

 time in mere determination, and partly because the use of 

 statistical methods is prone to provoke irrelevant criticism 

 from mathematicians with whom the mere biologist cannot 

 fairly compete. At the same time it is clear that the 

 frontier of Mendel's territoiy is not demarcated by any 

 special character, and — with all their experimental 

 disadvantages — the only characters which admit of 

 complete treatment are those which can be measured with 

 definable precision. 



There are many features of these complex results which 

 bear a tantalising resemblance to problems of human 

 heredity. 



Record system. — The examples to be quoted in 

 these pages are drawn from a systematic set of records. 

 These records are compiled from three sources, the Field- 

 Books, Field-Cards, and the Laboratory-Books, in which 

 the actual observations are entered. These are then worked 

 up at the end of the year in two ways ; first in the 

 Files, and secondly in the Ledgers. The Files consist of 

 printed forms, one to every plant, on which are entered all 

 particulars available ; the file-sheet of the plant shown in 



