DEVELOPMENT OF LYMPHATICS IN ANURA 89 
was specified for the frog; yet, | am inclined to believe that even 
in frog larvae the first hint of a lymph heart may be demonstrated 
earlier by means of reconstructions, which, if accurately executed, 
71. ES 
ae a 4 
cerd.post. = pr oneph. card. post. 
Fig. 15 Photomicrograph of a transverse section through the left lateral and 
anterior trunk region in a 5-mm. embryo of Bufo vulgaris (IK. E. C., series B 44, 
slide 2, section 142). X 340. (Zeiss Apochromat. Obj. 8 and Compensat. Pro- 
ject. Oc. 4). 40. seg., 4th intersegmental vein; med. and lat. v. card. post., medial 
(subeardinal) and lateral divisions of the posteardinal vein; d. proneph., proneph- 
ric or primary excretory duct; ao., aorta; ch., chorda dorsalis; myot., myotome; 
ep., epidermis. 
bring to view significant twists and turns and other topographical 
details that frequently escape the strictest scrutiny of serial sec- 
tions. However, the relative time at which the lymph heart 
arises is a matter of little importance; we are interested more in 
