C'harU'8 R. BanUrii 291 



become differentiated the portions of the foot-plate between them serve 

 for a short time to form a thick web, Fig. 67. 



Prochondrium period. — Schomburg gives a detailed account of the 

 early differentiation of the anlages of the bones of the foot and illustrates 

 his belief as to their nature by several diagrams. Unfortunately he docs 

 not picture the wax-plate reconstructions which he reports having made 

 of a number of early embryos. In Prof. Mall's embryos I find no evi- 

 dence of the archipterygium-like conditions which Schomburg describes. 

 While it may be true that the somewhat slow development of cartilage in 

 the tarsus is owing to the great alterations from primitive conditions 

 which the human foot has undergone during its phylogeny, and to a cer- 

 tain extent has to repeat during its ontogeny, still the development of 

 the bones of the foot is far more direct than Schomburg's diagrams 

 indicate. In the embryos studied I also fail to find the rudimentary 

 tarsal t)ones described by v. Bardeleben, 83, 85. I have examined six 

 embryos between 15 and 20 mm. long without finding a trace of either 

 the OS intermedium tarsi or the triangularis tarsi. In only one instance 

 have I found the I cuneiform distinctly portioned out into dorsal and 

 plantar divisions by a lateral fissure. Study of adult variation statistic- 

 ally, as so admirably carried out by Pfitzner, 96, for the foot, coupled 

 with comparative anatomy, in this, as in so many other fields, throws 

 more light on a possible phylogeny than is gained from ontological 

 investigation. 



Embryo CXLIY, length IJ^ mm., is, of those I have studied, the 

 youngest showing definitely tarsal and metatarsal elements. The 

 general form of the skeleton is shown in Figs. and 6. The differentia- 

 tion of the tarsal elements is difficult to make out, that of the metatarsals 

 is clear. Webs between the latter still persist, Fig. 67. Webbed digits 

 are sometimes found in the adult (Eobertson). 



It is to be noted that the elementaiy condition of the foot of CXLIV 

 corresponds with none of the diagrams given by Schomburg. On the 

 whole the cartilagenous anlages have a position much more nearly resem- 

 bling the adult. Embryo XLIII, length 16 mm., exhibits pedal char- 

 acteristics almost identical with those of CXLIV. 



It may here be mentioned that in none of the embryos I have studied 

 is the fibula so long as the tibia. Schomburg states that at first it is 

 longer. 



The metatarsals when first formed are spread wide apart and gradually 

 become approximated. The diagrams of Schomlnirg indicate a different 

 condition. 



