THE GASTRAEA-THEORY, ETC. 143 



arrange themselves. The brilliant and pregnant works of 

 Johannes Miiller and Heinrich Rathke, which immensely 

 enlarged ovir knowledge, especially among the lower animals 

 have kept themselves quite entirely to this path ; and 

 the most important work next to Baer's essential work, 

 which has dealt with the history of development in animals, 

 the very valuable ' Untersuchungen iiber die Entwickelung 

 der Wirbelthiere,' of Robert Remak (1851), must be looked 

 upon as an immediate continuation of Baer's researches in 

 this path. Its principal original value consists in this, 

 that the empirical philosophical investigations into the 

 details of embryology are removed from the section treating of 

 organs to that treating of histology, and that the justness of 

 the principles which Baer had posited in reference to the 

 individuals of the second order — the organs, were put by him 

 to the proof on the individuals of the first order — the cell. 

 Through the wider extension which Remak gave to the 

 germ-lamella theory it was at the same time raised to be 

 the starting point of histogenesis. 



If, on the one hand, the manifest correctness and perfect 

 validity of the ideas thus introduced by Wolff and Baer into 

 tlie history of development, and before all the fundamental 

 germ-lamella theory show themselves most decidedly by the 

 immense influence which they exercised on the very im- 

 portant investigations of their numerous successors ; so, on 

 the other hand, not less, though in a negative way, was their 

 importance shown by the weakness of the few opponents 

 who attempted to leave the path which had been pointed out 

 to them, and to strike out into a new and quite different 

 direction. The most pretentious of these attempts proceeded 

 from Carl Boguslaus Reichert, who endeavoured, in nume- 

 rous separate papers, but more especially in his Memoir on 

 * das Entwickelungsleben in Wirbelthier-Reich.' (1840), and 

 in his ' Beitragen zur Kenntniss des Zustandes der heutigen 

 Entwickelungsgeschichte' (1843) to reject the germ-lamella 

 theory, and with it the essential first principles of zoogenesis 

 depending thereon, and in their stead to set up a wild con- 

 glomerate of fantastic conceits, that do not for one second 

 deserve the name of scientific hypotheses, still less to be 

 called theories. Whereas the before-mentioned authorities 

 on embryology had laboured, by clearly expressing their ideas, 

 and by the exposition of the laws of development, to bring 

 both light and order into the chaotic fulness of embryological 

 facts, and to explain by falling back on simple principles 

 the complicated phenomena met with, Reichert attempted to 

 reverse this process, and thereby to obtain a temporary 



