Problems, Concepts and Their History 



13 



Von Baer's own embryology, for the first 

 time, for all of its emphasis on the relation- 

 ship of the special to the general, was an 

 embryology in which the metaphysical be- 

 came subordinate to the biological in the 

 sense of modern embryology, and became an 

 embryology which proceeded from embry- 

 ological facts and phenomena towards em- 

 bryological concepts, rather than in the 

 reverse direction; and von Baer, in accom- 

 plishing this feat, made one of the greatest 

 advances in all biological history. His force 

 of intellect, his consequent self-mastery and 

 ability to free himself to develop beyond the 

 thought in which he was trained, are vtn- 

 matched in biological progress. He could 

 emancipate himself from the thinking of his 

 times more than Vesalius, more than Harvey 

 before him; more than Darwin after him, 

 and though perhaps not in an analytical 

 sense, yet in a synthetic sense more than 

 Mendel to follow. 



His courage to maintain his own inde- 

 pendence of thought may have been fed by 

 his century's new kind of awareness of the 

 individual, with its philosophical back- 

 ground from Leibniz and Kant, developed 

 by Fichte and Schelling and Hegel, and its 

 translation diu-ing the eighteenth century 

 into more widespread acceptance than ever 

 before of the significance of freedom of indi- 

 vidual action. Von Baer absorbed the con- 

 cept of independence: "Deswegen ist auch 

 das wesentlichste Resultat der Entwickelung, 

 wenn wir sie im Ganzen iibersehen, die 

 zunehmende Selbststdndigkeit des werden- 

 den Thiers" {ibid., I, 148), he wrote, and 

 he concentrated on the individual. Wesen- 

 heit was all: "Die Wesenheit des Thiers 

 beherrscht die Ausbildung. . . . Die Wesenheit 

 . . . der zeugenden Thierform beherrscht die 

 Entwickelung der Frucht" (ibid., 1, 147-148). 

 But like Aristotle and Goethe, von Baer 

 was obsessed with the dynamic and func- 

 tional qualities of the organism as a whole. 

 "We know that all the functions of the per- 

 fect animal body contribute to a general re- 

 sult, — to the life of the animal," we have 

 already quoted, "but also that the general 

 mass manifests the total life (for animal life 

 is always a totality)." "Die Entwickelungs- 

 geschichte des Individuums ist die Ge- 

 schichte der wachsenden Individualitat in 

 jeglicher Beziehung" {ibid., I, 263), he 

 wrote too; and he thovight of the growing 

 individual too, like Goethe, in respect to a 

 larger whole; to him the palm, "dem es vor- 

 behalten ist, die bildenden Krafte des thier- 

 ischen Korpers auf die allgemeinen Krafte 



oder Lebensrichtungen des Weltganzen 

 zuriickzufiihren" {ibid., I, xxii). 



Like Goethe, he could say, and in almost 

 the same figure of speech, that "die Ge- 

 schichte der Natur ist nur die Geschichte 

 fortschreitender Siege des Geistes ilber den 

 Stoff" (1864, pp. 71-72), but he meant it in a 

 different context (1828, I, 263-264): 



Hat aber das eben ausgesprochene allgemeinste 

 Resultat Wahrheit und Inhalt, so ist es Ein Grund- 

 gedanke, der durch alle Formen und Stufen der 

 thierischen Entwickelung geht und alle einzelnen 

 Verhaltnisse beherrscht. Derselbe Gedanke ist es, 

 der im Weltraume die vertheilte Masse in Spharen 

 sammelte und diese zu Sonnensystemen verband, 

 derselbe, der den verwitterten Staub an der Ober- 

 flache des metallischen Planeten in lebendigen For- 

 men hervorwachsen liess. Dieser Gedanke ist aber 

 nichts als das Leben selbst, und die Worte und Syl- 

 ben, in welchen er sich ausspricht, sind die verschie- 

 denen Formen des Lebendigen. 



But if von Baer's outlook, like Goethe's, 

 was cosmic in scope, his inspiration was the 

 detailed and specific study of the developing 

 form of the individual living embryo. Like 

 Aristotle, he accepted form as inseparable 

 from the formed. The advantage of refine- 

 ment bestowed by time to his philosophical 

 and technical method, as compared with 

 Aristotle's, enabled him to concentrate more 

 on the formed, which was biological ma- 

 terial, than on form as such and metaphys- 

 ical; and in so advancing he became the true 

 synthetic genius which Goethe had aspired 

 to be, "der grosste unter uns in Vergangen- 

 heit, Gegenwart und weiter Zukunft" (Roux, 

 1889; cited from Roux, 1895b, II, 25). 



EMBRYOLOGY AND EVOLUTION: 

 DARWIN AND HAECKEL 



It has been said that all biology since 

 Darwin has been a commentary on the 

 Origin of Species. Embryology would be in 

 a more advanced position than its present 

 one if one could claim that all embryology 

 after von Baer represented a commentary 

 on his great treatise. It is true that immedi- 

 ately following his time, even during it, 

 great strides were made in the amplification 

 and refinement of his teachings. Rathke, in 

 particular, whose quality of mind was in 

 many ways like that of von Baer, made par- 

 ticular advances in demonstrating the exis- 

 tence of the germ layers in invertebrates as 

 well as vertebrates and in discovering the 

 presence of gill slits in the mammalian em- 

 bryo. The universality of the germ layers 

 was given new meaning with the enuncia- 

 tion of the doctrines of universality of proto- 



