Key 



: 





1. 



In the egg occurs 



10 



2. 



Radiant development (?) 





3. 



Sprial development 



11 



4. 



Symmetrical development 



12 



5. 



Double symmetrical 



13 





development 



14 



6. 



Animals of peripheral 



15 





type 



16 



7. 



Animals of massive 



17 





type 



18 



8. 



Animals of elongated 



19 





type 



20 



9. 



Vertebrate animals have 

 vertebral column, spinal 



21 





plates, nervous tube, 



22 





branchiate slits and 



23 





acquire 



24 



Branchiate fringe; the 



latter 



Do not form actual lungs 



Form lungs 



Skeleton does not ossify 



Skeleton ossifies 



Carlilaginous fish 



Bony fish Amphibia 



Growing urinary sac 



No umbilical cord 



There is umbilical cord 



No wing and air sacs 



There are wing and air 



sacs 



Reptiles 



Birds 



Mammals. 



357 



