APPENDIX 377 



"wards of a diverticulum of the cesaphagus, which 

 became ultimately a swim bladder or a lung."* 



" The segmentation of the limbs of vertebrata is a 

 simple mechanical problem. Paleontology and em- 

 bryology concur in proving that the limbs originated 

 in primitive folds in the external integument, and 

 that their connection with the internal skeleton was 

 ■of later accomplishment, has been shown by Widers- 

 heim." f The origin of the limbs of vertebrates, 

 with their complicated structures, is a very difficult 

 problem. Embryology, I believe, teaches nothing on 

 this subject, nor does paleontology, as far as I have 

 been able to learn, show that the " limbs originated 

 in primitive folds in the external integument." 



The author claims that the original limbs were 

 *' slender- rods which were segmented by interruptions 

 at suitable points." Strange indeed is it that folds of 

 the skin were developed into slender segmented rods. 

 One would have expected that such folds would give 

 rise to broad limbs of some kind. 



Again, he says that "the articulations of the fin- 

 rays of fishes, as shown by Ryder, are fractures, due 

 to flexures during motion in the water medium." 



By the process of fractures, I understand that the 

 author intends to explain the origin of the joints in 

 limbs. If this is true, it indeed becomes marvelous 

 when we ti - y to account, in this way, for the origin of 

 all the joints in the arms and hands, legs and feet of 

 man. Between one and two hundred fractures, all 

 made by accident, with exact regularity in the corre- 

 sponding parts of limbs, must have occurred. If this 

 is true, what has become of the doctrine of chances? 

 How have four complex limbs, alike in pairs, and all 

 four closely alike, with a great, number of corre- 

 * Page 363. t Page 366. 



