222 K. E. VON BAER. — PHILOSOPHICAL FRAGMENTS. 



animal which the embryo had to pass through, but simply as a 

 partial stoppage at an earlier stage of their own development. 

 At times unquestionably there exists an obvious similarity with 

 some permanent form in particular parts ; but it is as readily 

 demonstrable that this similarity is not the condition of the mal- 

 formation, but the result of other relations, either, — 1st, because 

 that form is nearer the fundamental type, in which case any 

 stoppage at an earlier period of development must necessarily 

 approximate the higher form to it ; or, 2ndly, because the altered 

 formative conditions may approximate the formative conditions 

 of the same part in another animal. Thus, for example, the nose 

 in Man is sometimes elongated into a proboscis, which reminds 

 one of the snout of a Pig. But the human nose never passes 

 through any stage of development in which it resembles the 

 snout of a Pig ; on the other hand, the Pig^s snout, at the fourth 

 week of embryonic life, is not only similar to that of a human 

 embryo at an early period, but is in fact much more like the 

 nose of the adult Man than at a later period. 



This relation agrees perfectly with the general law. The nose 

 of air-breathing Mammals in general does not project beyond 

 the jaw. Both the peculiarity of the Pig's snout, therefore, and 

 that of the human nose, arise subsequently without any transi- 

 tion of the one form through the other. If then a Man has the 

 snout of a Pig, it is no arrest of development, but the conse- 

 quence of an abnormal development, which has a result like that 

 in the Pig, where it is normal. While we are speaking of the 

 abnormal forms of the nose, I will call to mind the "Wolf's 

 jaws," an indubitable arrest of development, but which is cer- 

 tainly no stoppage at any earlier form of animal. 



Second Corollary. — Application of the present View to the 

 Determination of the separate Organs in the different Forms 

 of Animals. 



A closer acquaintance with the history of development will 

 sooner or later furnish us with the sole safe grounds in the de- 

 termination of the fitting denominations for, and in forming a 

 just judgment of, the organic parts of the different forms of 

 animals. At present a little may be done in this direction. 



Since, in fact, every organ becomes what it is only by the 



