Problems, Concepts and Their History 



11 



were to begin to build constructively upon 

 Wolff's concepts; and the fact that they could 

 start to do so is related probably to Wolff's 

 own compatibility with N aturphilosophie . 

 Wolff's epigenesis had started as conceptual, 

 his concept, and the results of his own micro 

 scopic examinations, led those who were to 

 follow him to the material where they could 

 build upon what he had postulated and dem 

 onstrate a mechanism of the process of change 

 he had postulated. 



The group consisted of Pander, who first 

 demonstrated the existence of the three pri- 

 mary germ layers in the embryo of the 

 chick; of Goethe's friend D' Alton, who acted 

 as artist; and of von Baer, who generalized 

 Pander's germ layers for other animals and 

 who in so doing generalized the science of 

 embryology itself. 



Pander's advance was a great one, in a 

 way, in terms of independence of thought; 

 and his achievement, in an environment of 

 overgeneralization, in being able to concen- 

 trate on describing specific processes of de- 

 velopment in a single form without drawing 

 far-fetched analogies, was considerable. But 

 Pander could not, or did not, carry through, 

 and it was left to von Baer, or rather, von 

 Baer took it upon himself, to broaden the 

 base by the examination of more varied 

 material. 



With his inspiration from the romantics, 

 he looked at the diverse material with a 

 question in his mind as to its comparability; 

 and he came away from it with the convic- 

 tion that the comparability was there, in 

 terms of origin (hence the discovery of the 

 mammalian egg), and in terms of process in 

 the similarity of the formation of the germ 

 layers and in the derivation of similar or- 

 gans from comparable layers in the different 

 vertebrate forms. He demonstrated develop- 

 ment to be at once from homogeneous to 

 heterogeneous, from general to special, in all 

 the forms that he studied. Though his feat 

 was an overwhelmingly intellectual, not 

 technical, achievement, his great advance 

 was the extent to which he based his con- 

 clusions on the zealous and acciu-ate and 

 untiringly meticulous microscopic observa- 

 tions on a wide variety of animal material: 

 Beobachtung preceded Reflexion in his title. 



His emphasis on comparability involved, 

 to be sure, as did that of the other Natur- 

 philosophen, an emphasis on Type: "Zufrie- 

 den wiirde ich seyn," he wrote, "wenn man 

 es als meinen Antheil betrachtet, nachge- 

 wiesen zu haben, dass der Typus der Orga- 

 nisation die Entwickelungsweise bedingt" 



(1828, I, xxii). But he meant by Type some- 

 thing different than the others: 



Vor alien Dingen mache ich darauf aufmerksam, 

 dass man den Grad der Ausbildung des thierischen 

 Korpers mid den Typus der Organisation unter- 

 scheiden muss. Der Grad der Ausbildung des thieri- 

 schen Korpers besteht in einem grossern oder gerin- 

 gern Maasse der Heterogenitat der Elementartheile 

 imd der einzelnen Abschnitte eines zusammenge- 

 setzten Apparates, mit einem Worte, in der 

 grossern histologischen und niorphologischen Son- 

 derung. . . . Typus neime ich das Lagenongsver- 

 haltniss der organischen Elemente und der Organe 

 (1828, I, 207-208). 



Our persuasion, that the grades of development 

 must be distinguished from the types of organiza- 

 tion, is founded upon the following considerations: 

 — We know that all the functions of the perfect 

 animal body contribute to a general result, — to the 

 life of the animal; but also that the general mass 

 manifests the total life (for animal life is always a 

 totality). . . . With a greater separation and more 

 complete independence of these functions is com- 

 bined a greater differentiation of the body into or- 

 ganic systems, and of these systems again into sep- 

 arate more individualized sections. In this consists 

 the higher development of the animal body. 



But the mode in which these organs of the animal 

 body are united together, is a wholly distinct mat- 

 ter. And it is to this manner in which the organic 

 elements are combined that we give the name of 

 Type. Every type may be manifested in higher and 

 lower degrees of organization; the type and the 

 grade of development together determine the spe- 

 cial forms (1826; cited from 1853 edition, pp. 178- 

 179). 



Here there is an implication still of the 

 Type and Archetype of the Naturphiloso- 

 phen, but it is becoming more Type in com- 

 mon with Aristotle's form in the sense of 

 potentiality. While von Baer has adopted a 

 concept from N aturphilosophie, he has de- 

 veloped it further; for von Baer, it is the 

 embryo, not the Idea, that is becoming the 

 type. It is irrelevant for our purposes that 

 he considered the primary types to be those 

 of the vertebrate, the annulate, the radiate 

 and the mollusk (the double symmetrical, 

 the longitudinal, the radiate and the spiral; 

 polarity and symmetry were a central idea, 

 both problem and metaphysical reply to it, 

 for the Naturphilosophen as for modern bi- 

 ologists). What is significant is that he could 

 regard them, rightly or wrongly, as separate 

 types of extant, visible, dissectable and ob- 

 servable animals perceived by his sense or- 

 gans. This is phenomenological type, type 

 not in an Idea but present as structure in an 

 adult organism, and if masked there, some- 

 times discernible in the structure of the 

 embryo; and thereby the relationship of 



