Lect. I.] LAEVIFOEM EMBRYO OF THE MOLE. 



15 



Know one, know all ; one diagram would represent 

 all, one description serve for all. 



Such a stage, moreover, gives us a form extremely 

 like that of any other gill-less type — bird or reptile ; 

 while to make it into a semblance of the lower aquatic 

 types, more '^visceral arches," with more and more 

 gaping clefts, are all that would have to be added. 



In all we have the curved, larviform creature, with its 



TT'^C 



Fig. 1. — Embryo of Mole {Talpa europwa, 1st stage), 

 magnified 12 diameters. 



large brain-lobes bent under, in front ; its tail-end bent 

 under, behind; its solid front folds, its rudimentary gill- 

 openings, and its paddle-sha^Dcd limb-buds. But the 

 characters derived from its more immediate ancestry 

 soon show themselves. By the time the gaps in the 

 throat are filled up, and the embryo has doubled its 



