INCUBATORIAL AREA IN ECHIDNA 



29 



very soon take their own course. These facts 

 are very clearly illustrated in the series o£ 

 drawings of successive stages represented in 

 Figs. 12a, 12b, 13a, and 13b. 



Fig. 12a represents a section of primary- 

 primordium in Semen's Stage 51, of which 

 Fig. 11b gave a complete view. The hair 



Fig. 12b.— Echidna: Tkansvkkse Section through 

 THE Incubatorial Area OF Semon's Embryo, 

 Stages 51 and 52. 



Dr, Gland area ; dr, small gland bud. 



primordia of the surrounding skin,' with the 

 sweat-gland outgrowths now first appearing 

 {sdr), and the first hair buds {ha) within the 

 primary-primordium, are clearly shown. In 

 Stages 51 and 52 (Fig. 12b) there is a further 

 growth of the hair follicles within as well as 

 without the primary-primordium, and likewise 



