4 ARKIV FÖR ZOOLOGI. BAND 10. N:0 21. 



hind toe, or even with »double spurs», that is such a rudi- 

 ment and a praehalliix as well. Such rudiments occur very 

 of ten in »Dachshunde», several races of Hare hounds or 

 harriers etc. but in all cases observed by the present writer 

 these rudiments are very different in appearance. They are 

 very loosely attached to the foot, often they appear to häng 

 in the skin only. In consequence of this they cannot be 

 worn and thus the claw itself is strongly hypertrophied and 

 much curved in a semicircle, or more, although it is com- 

 paratively thin and pointed at the end. Veterinary surgeons 

 with whom I have spöken about these spurs and who have 

 had a rich experience in removing them on a number of 

 dögs agree in sta ting that, as a rule, these »spurs» are only 

 loosely connected with the foot. Often the claw alone forms 

 the whole rudiment. Very often the distal phalanx is deve- 

 loped, sometimes also the basal phalanx. It may happen 

 that these phalanges by a strand of connective tissue are 

 connected with the metatarsus, or even, although seldom, 

 that a thin metatarsal bone is developed. It is thus a great 

 variation to be found with regard to the internal constitu- 

 ents of these rudiments, as indeed generally is the case with 

 rudiments without function. 



From these statements may be concluded that the first 

 hind toe as it is developed in the fox from Biskops-Arnö 

 represents a much less rudimentary stage than usually, or 

 as a rule, the »spurs» of domestic dögs do. There is a very 

 great interest connected with this fact, because it proves 

 that an organ which has been completely löst during the 

 phylogenetical development of a species of mammals suddenly 

 can reappear again after an even phylogenetically speaking 

 extremely long period of suppression. This is contrary to 

 the general opinion among biologists. It has been regarded 

 as an undisputed law that an organ which once has been 

 reduced to complete disappearance cannot be developed 

 again, and far reaching conclusions have been based on this 

 theory. There is no doubt that it generally hold strue, but 

 an exception is therefore the more instructive. 



It is true that during the ontogenetic development in 

 embryological stages probably traces of the first hind toe 

 might occur, altough I have not had the opportunity of 



