190 K. K. vox BAER. — PHILOSOPHICAL FRAGMENTS. 



§ 2. Doubts and Objections. 



At an early period my attention was directed to the mutual 

 relation of the permanent forms of animals ; and the first thing 

 that appeared obvious to me was, that this relation could in 

 nowise be considered as a uniserial progressive development. 

 But a uniserial progressive development, if only as a logical 

 conception, appears to be absolutely necessary for the permanent 

 forms of animals, if they are repeated in the development of the 

 individual. 



I therefore regarded this doctrine with mistrust, and kept it 

 constantly in mind in investigating the development of the chick, 

 in the persuasion that the continued observation of the develop- 

 ment of a single species of animal must yield a more certain 

 decision than a multitude of single unconnected comparisons. 

 As, however, my observations convinced me that the essential 

 character of the vertebrate animal arises very early in the chick, 

 and regulates the whole course of its development, I so early as 

 the year 1823 expressed my doubts in the form of an academical 

 disquisition*. Nevertheless it seemed fitting not to speak pub- 

 licly concerning them until 1 could present a series of observa- 

 tions. My conviction with regard to that law, indeed, was more 

 • a negative one. I now believe that I can replace it by another; 

 and the first part of this collection offers, I think, a proper op- 

 portunity for the development of the latter. 



It will not be superfluous first of all to bring forward a few 

 objections to the view just alluded to, which might be drawn 

 from the previous investigations of embryos, and which might 

 serve to raise doubts in the minds of those readers who are com- 

 pletely devoted to it. Not attempting a complete development 

 of these doubts, I shall content myself with a few brief indi- 

 cations. 



In the first place, I was led to reflect, that we know the de- 

 velopment of hardly any but the highest forms, the development 

 of Mammalia (including Man) and that of Birds. In whatever 



♦ Dissertatio de fossilibus Mammalium reliquiis. Regiomont. 1 823, 4to. To 

 which is appended the thesis, Legem a naturce scrutatorihiis proclamatam , evo- 

 lutionem quam ptbna cetate quodque subit animal quam in animalinm serie ob- 

 servandam putant, respondere, a natura alienum esse coniendo. 



