218 SECTIONAL ADDRESSES. 



germ- plasm has been shown to be subject to temporal influences must not 

 be belittled. A true mutation is not eternal. Our descendants may be 

 able to dispense with haemoglobin. Whether the hereditary melanism 

 that in certain moths, it is said, can be induced by food infected with 

 manganese is something more than such parallel induction, I hope there 

 may be some present who can say. 



Physiological inquiry is a stream that has many sources ; its waters 

 gather from quarters far removed from one another. A marvellous meeting 

 took place in the early years of this century when the forgotten experi- 

 ments of Mendel came to the surface again, and found corroboration in 

 the cytological studies that from about the same time had pursued their 

 slow, obstructed way above-ground in the endeavour to elucidate the 

 changes in the nucleus of maturing germ-cells. In a resting germ-cell the 

 chromosomes form an even number, characteristic for the species ; they 

 consist of half that number of pairs of homologues, one of each pair 

 descended from the paternal element in the last zygosis, the other from 

 the maternal. At one of the cell divisions by which the germ-cell gives 

 rise to the mature gamete, with half the characteristic number of chromo- 

 somes, there occurs a segregation of the two members of each pair so 

 that they pass into different gametes ; the exact cytological equivalent 

 of Mendelian segregation of allelomorphic pairs of characters. To-day 

 the study of genetics and of the ' topographical anatomy of the chromo- 

 somes,' with its " groupings ' and ' crossings over,' seems to call out for 

 chemical assistance. It may be that in the lifetime of some of us those 

 confluent streams of thought and experiment are to be joined by yet 

 another that rises in the vast, remote, and, as it must appear to some, 

 muddy swamps of physiological chemistry ; and it then, forgetting its 

 ' foiled, circuitous wanderings,' will form with them a ' majestic river, 

 brimming and bright and large." 



