152 MAMMALIAN DESCENT. [Lect. VI. 



is even now revealed, the connective-tissues are all in 

 a generalised state ; cartilage is promised, l)iit it is only 

 marked by the greater crowding of the cells, and not by 

 any definite modification, as yet. Where general embry- 

 ology ends, there s^^ecial morphology begins. My proper 

 cue is the formation of clear or hyaline cartilage ; the 

 true primary skeletal material. We get that by the time 

 the embryo Mole is the size of a Blue-fly's larva ; this 



W+(n; 



Fig. 13. — Embryo of Mole {Talpa eurojma), magnified 

 4 diameters (3d stage). 



is the first of ten stages in which I have followed 

 the details of the anatomy of the head. 



I do not say skull, merely; given a dry skull, prepared 

 ])y an assistant, and an artist to make the drawings 

 for you, and you have a short and ready method for 

 becoming a comparative craniologist. But that is not 

 enough for this generation of workers. We mean by 



