April 21, 1922] 



SCIENCE 



421 



13. The principle of associative inlieritance — 



linkage. 



Discovery by Bateson in sweet peas. — 

 Elaboration by Morgan and others in Dro- 

 sophila. — Extension to other plants and 

 animals by various workers. — The chiasnia- 

 type theory as an explanation of the mech- 

 anism of linkage and crossing over. — 

 Illustrations of various linkage phenomena. 



14. The inlieritance of quantitative characters. 



The facts. — The interpretations that have 

 been offered. — The multiple factor hypothe- 

 sis. 



15. The statistical study of variation. 



Calculation and uses of the ordinarj' bio- 

 metrical constants. 



16. Correlation. 



Calculation and uses of the coefficient of 

 correlation. 



17. The pure line concept. 



Johannsen's selection experiments and con- 

 clusions. — Confirmation and extension by 

 other workers. 



18. The role of selection in plant and animal 



breeding. 



Effect of selection m populations of self- 

 fertilized and cross-fertilized plants and 

 with animals under various systems of 

 mating. — Selection from the point of view 

 of the animal breeder. — Modifying factors. 



19. Inbreeding and outbreeding. 



The conflict of views. — Experimental evi- 

 dence in both plants and animals. — Inter- 

 pretation of the results of inbreeding. — 

 Heterosis and its utilization in plant and 

 animal production. 



20. Non-Mendelian inheritance. 



Cytoplasmic and maternal inheritance. — 

 Chimeras. 



21. The mutation concept. 



The DeVriesian view. — The modern view. — 

 Point or factor mutations and multiple 

 allelomorphs. — Eegional mutations. — Chro- 

 mosome aberrations. — Bud variations. — 

 Attempts to induce mutations. 



22. The mode of evolution from the mutation 



point of view. 



23. Eugenics. 



The application of genetic principles to 

 race improvement. — Limitations. 



C. B. Hutchison 

 Cornell University 



LAMARCK, MIRBEL AND THE CELL 

 THEORY 



It seems to have escaped the notice of writers 

 of text books on biology and the history of 

 science, even in France, that the cell theory in 

 broad outlines was taught in Paris at the very 

 opening of the nineteenth century, forty years 

 before Sehleiden and Schwann published their 

 famous epoch-making work. 



Lamarck stated clearly in his "Philosophie 

 Zoologique," 1809, that all plants and animals 

 are composed essentially of cellular tissue, 

 without which "no living body would be able 

 to exist nor could have been formed." "Since 

 1796," he says, "I have been accustomed to set 

 forth these principles in the first lessons of my 

 course." 



Lamarck's clear and positive statement of the 

 fundamental importance of cellular tissue, like 

 his theory of evolution, unfortunately was not 

 supported by an array of well authenticated 

 published facts. Lamarck's conception was that 

 cellular tissue (epidermal and connective), en- 

 closing the organism and its parts, is the matrix 

 in which the fluid living matter is shaped into 

 organs, by physico-chemical forces acting upon 

 it from without. 



Mirbel, his younger colleague at the museum, 

 adopted the cellular tissue theory, and brought 

 to its support from the field of botany a splen- 

 did body of facts, to which long afterwards 

 both Sehleiden and Schwann allude. To Mir- 

 bel plants are made of a folded membranous 

 cellular tissue, with slow circulation of fluid 

 among the cells through intervening pores. 



Dutrochet, in 1824, introduced into the theory 

 the idea of the individuality of the cell, of 

 which all plants and animals are composed, but 

 unfortunately he had no standard by which to 

 decide what is, or what is not, a cell in the 

 animal. The universally present nucleus had 

 not yet been discovered and the cell thus, so 

 to speak, standardized. Hence in matters of 

 detail, he went somewhat astray, but he was a 

 most enthusiastic supporter of the cell theory as 

 he knew it. 



Robert Brown, as a by-product of a work 

 on fertilization in Orchids and Milkweeds, 

 described the universal occurrence of cell nuclei. 



