220 K. E. VON BAER. PHILOSOPHICAL FRAGMENTS. 



type necessarily becomes considerably modified. The Worms, 

 the Myriapoda, have an evenly annulated body, and are nearer 

 the type than the Butterfly. If then the law be true, that in 

 the course of the development of the individual the principal 

 type appears first, and subsequently its modifications, the young 

 Butterfly must be more similar to the perfect Scolopendra, and 

 even to the perfect Worm, than conversely the young Scolo- 

 pendra, or the young Worm, to the perfect Butterfly. Now if 

 we leave out of sight the peculiarities of the Worm, the red 

 blood, &c., which it attains at a later period, we may readily say 

 that the Butterfly is at first a Worm. The same thing is ob- 

 vious in the Vertebrata. Fishes are less distant from the fun- 

 damental type than Mammalia, and especially than Man with 

 his great brain. It is therefore very natural that the Mam- 

 malian embryo should be more similar to the Fish than the em- 

 bryo of the Fish to the Mammalian. Now if one sees nothing 

 in the Fish but an imperfectly developed Vertebrate (and that 

 is the baseless assumption to which we referred), the Mammalian 

 must be regarded as a more highly developed Fish ; and then it 

 is quite logical to say that the embryo of a vertebrate animal is 

 at first a Fish. Hence it was that I asserted above ( 1.), that 

 the view of the uniserial progression of animals was necessarily 

 connected with the prevailing idea as to the law of development. 

 But the Fish is not merely an imperfect vertebrate animal ; it 

 has besides its proper ichthyic characters, as development clearly 

 shows. 



But enough ! I have attempted, in embodying the course of 

 development, to show also, that the embryo of Man is unques- 

 tionably nearer to the Fish than conversely, since he diverges 

 further from the fundamental type ; and upon this ground alone 

 has much been inserted that is problematical, as the umbilical 

 attachment of the Monotremata. In detail, this representation 

 can as little exhibit all the relations justly, as any other repre- 

 sentation of organic relations upon a plane surface even if the 

 investigation were complete, instead of being just begun. 



Let us sum up the contents of this section as its conclu- 

 sion. The development of an individual of a certain animal 

 form is determined by two conditions: 1st, by a progressive 

 development of the animal by increasing histological and mor- 



