43 Wax reconstruction of the thyreoid gland of an early transforming larva, 

 showing the relation of follicles one to another, and to the external (inferior) 

 jugular vein, and the small medial twig from the sternohj'oideus muscle, which 

 forms a rete mirabile within the follicular mass. Note the large size of follicles. 

 (kSee fig. 31, which is a cross section of this gland for details of the internal rela- 

 tionships.) (X 62) 



44. Wax reconstruction of the left postbranchial body of 26 mm. larva, from 

 above. (X 200) 



45 Wax reconstruction of the thyreoid anlage of 8 mm. larva, showing its con- 

 nection with the pharyngeal epithelium anteriorly at the point where the hj^o- 

 mandibular pouch is extending laterally. Notice also, the position of the copula 

 (co.) and the hyoid and first branchial cartilage anlagen just dorsal to it. (X 50) 



46 Wax reconstruction of the hyoid apparatus of the late transforming larva 

 which is almost that of the adult condition, showing the relative positions of the 

 thyreoid (tr.) and thytnus (i) glands to the cartilages. (X 50) 



47 Wax reconstruction of the ventral pharyngeal region of 39 mm. larva, 

 (right side), showing the position of the thyreoid gland in this stage to the bran- 

 chial cartilages and blood vessels, (about X 30) 



680 



