INTRODUCTION 13 



their modifications. 1 Thus, in the Studien zur 

 Blatter Theorie, published by Richard Hertwig and 

 myself, I combated the supposed law that the 

 germinal layers histologically were primitive organs. 

 Next, in a pamphlet entitled The Problem of Fer- 

 tilisation: a Theory of Heredity, I attempted to 

 disprove the principle of His that there were 

 organ-building foci in the germ. In my treatise 

 Oil Ovogenesis and Spermatogenesis in the 

 Nematodes, I declared against the suppositions 

 involved in Weismann's doctrine of the germplasm, 

 and sharply distinguished the theory, simul- 

 taneously propounded by Strasburger and myself, 



1 The ideas expressed in this book may be found, in an elemen- 

 tary condition, in various publications of my own, and written in 

 conjunction with my brother, Richard Hertwig : Oscar and Richard 

 Hertwig, Die Actinicn ; Jena, 1879 (pp. 203-217). Oscar HertAvig, 

 Das Problem dcr Befruchtung und dcr Isotropic dcs Eies. cine 

 Tlicoricdcr Vcrcrbung ; Jena, 1884. Oscar Hertwig, Vcrgleich dcr 

 Ei- und Samcnbildungbei Ncmafoden, Arch. f. Mikrosk. Anatomic, 

 vol. xxxvi., 1890, pp. 77-128. Oscar Hertwig, Una and und Spincc 

 bifida, Arch. f. Mikrosk. Anatomic, vol. xxxix., 1892, pp. 476-492. 

 Oscar Hertwig, Aeltcrc und ncuere Entiricklungsthcoricn ; Berlin, 



1892. Oscar Hertwig, The Cell: Sonuenschein ; London, 1895. 

 Oscar Hertwig, Ueber den Wertli dcr ersten Furchungszcllen fur die 

 Oryartbitdtuig des Embryo, Arch. f. Mikrosk. Anatomic, vol. xlii., 



1893. The chief other writers to whom I refer are : Herbert 

 Spencer, Principles of Biology. Darwin, Pangcnesis, a Provisional 

 Hypothesis (in Variation of Plants and Animals under Domestica- 

 tion}. Haeckel, Die Perigcnesis der Plastidulc. Weismann, loc. ciL, 

 p. 8. Naegeli, Median isch - physiologische Theorie dcr Abstam- 

 nmngslehre ; Miinchen, 1884. Strasburger, Neue Untersuchungcn 

 ueber den Bcfruchtungsvorgang bei den Phanerogamenals GruncUagc 



fill- cine Theorie der Ze-ugung, 1884. H. de Yries, Intracellulare 

 Pangenesis. W. His, Unserc Kdrpcrform and dux pliysiologische 

 Problem Hirer Entstehung, 1874. W. Roux, loc. cit., p. 6. 

 Driesch, loc. cit., p. 48. 



