1450 LIFE : OUTLINES OF GENERAL BIOLOGY 



drop of protoplasm, which sometimes quiver in a "Browiiian 

 movement", due to their being jostled by the wandering molecules; 

 but these are less important than the ultra-microscopic particles, 

 which cannot be directly seen owing to their minuteness. Though 

 invisible, they are demonstrable by means of the ultra-microscope, 

 which reveals their diffraction discs or haloes of reflected light. The 

 multitudinous surfaces of these ultra-microscopic particles and 

 droplets afford opportunity for chemical and physical changes toB 

 occur, as the coast-lines of an archipelago of islands do for trading 

 and fishing, and this is what makes the colloidal state of protoplasm 

 so fundamentally important. It may be added that while Hardy 

 and others showed that the microscopic reticulum does not cor- 

 respond to the natural condition of the cell, there must be some 

 arrangements, probably of a film nature, which separate one area 

 of a cell from another so that different chemical processes go on 

 simultaneously. 



We must include among the great events in the history of 

 Biology the introduction of statistical methods, for it meant the 

 discovery of a new organon of research which, in the skilful hands 

 of Galton and Pearson, Weldon and Pearl, has made important 

 contributions to the study of variation, heredity, selection, and 

 population. 



One of the seed-ideas in Biology is the inter-relatedness of organ- 

 isms, and it may be particularly associated with Darwin. It was 

 no doubt in Gilbert White's mind when he wrote the famous letter 

 on earthworms, and in Sprengel's when he traced the colour signs 

 and wayposts, landing-stages and hand-rails that attract and guide 

 pollinating insects to the nectaries ; and there were not a few other 

 precursors and anticipators. Yet far beyond all these Darwin stands 

 pre-eminent in his vision of the correlation of organisms into the 

 world's wide, ever-weaving web of life, and he more and more dis- 

 cerned this as the essential drama of biology. As John Locke said, 

 everything is a retainer to some other part of Nature. Thus earth- 

 worms plough the fields and plant trees; the bee and the flower 

 become fitted together more intimately than hand and glove. The 

 missel-thrush sows the mistletoe ; the minnow nurses the freshwater 

 mussel; the pied- wagtail helps the sheep-farmer; and the squirrel 

 has its share in making the harvest a success. According to some 

 historians, the glory of Greece was partly dimmed by the intrusion 

 of malaria. As this disease is disseminated by mosquitoes, and as 

 the mosquito larvae are very effectively kept in check by minnows 

 and other small fishes, we see a new meaning in the exclamation, 

 "Ye Gods and little fishes!" Now it is not merely that these and a 

 thousand other linkages are interesting facts in ecology; they illus- 

 trate the evolution of a manifold Drama of Animate Nature which 

 has been in progress throughout geologic ages. Apart from para- 



