PLATE 5 



EXPLANATION OF FICiURES 



12 Transverse section of an 8 mm. toad embryo through a little more than the 

 right half of the territory ventral to the mouth cavity (cf. fig. 1). Series 27, slide 

 1, row 5, section 8. X 500. 



REFERENCES 



/. to I., plexiform anlage of sinus e.c, right external carotid artery 



j.d., right external jugular vein vi.n., muscle anlagen 



13 Transverse section of a 9 mm. toad embryo through the ventral region of 

 the head. Series 2. slide 1, row 8. section 5. X 300. 



REFERENCES 



I., multilocular anlage of sinus j-d., j.s., right and left external jugular 



t., s., tissue strands and trabeculae, veins 



remnants of walls between originally inc., mouth cavity 



independent channels 



192 



