LYMPHATICS IN FROG LARVAE 43 



The injections illustrated in figures 3 and 4 from the second 

 period of the frog, show the first lymphatics separated from 

 the veins (not transformed) in a relatively compact group, 

 distinguished from the veins by their pattern and relations, 

 with no suggestion of segmental arrangement. 



The two systems will be followed separately from this sec- 

 ond stage: the history of the lymphatics continued in detail 

 to complete the paper, while only a brief account at the end 

 will be allotted to the three first intersegmental veins, in con- 

 nection with figures 37 to 40 (see pp. 78-82). The question of 

 their continuity through the period of lymphatic formation 

 being answered in the early stages, a few later stages of the 

 veins will permit the reader to follow them in correlation with 

 the further development of the lymphatics, the two systems 

 being readily brought together in the pictures of correspond- 

 ing stages. The later venous injections are also of value as 

 pictures (figs. 37 to 40) of uninterrupted continuation of the 

 history of these veins in forming the anterior vertebral and 

 great cutaneous systems. The 7-mm. toad corresponding to 

 the larva next to be described in the series of injections of the 

 frog (see figs. 13, 14, 15 of this paper) is the first toad larva 

 for which reconstructions are presented of the anterior lymph 

 heart and its associated plexus of saccular vessels (veno- 

 lymphatics Kampmeier, '22, fig. 35). Posterior lymphatics 

 of the same specimen are also shown in another figure (Kamp- 

 meier, '25, fig. 13) with lateral and dorsal vessels in still 

 incompleted plexuses. 



That the 7-mm. larva of the toad is the first stage in which 

 tissue spaces are sufficiently definite to reconstruct as parts 

 of a system is indicated in Kampmeier 's figure 12 ('25) for 

 the posterior lymphatics of another 7-mm. specimen, where 

 only a few scattered sacs labelled rudimentary lymphatics 

 are found along the veins. The distal elements of the dorsal 

 and lateral lymphatics in the more complete reconstruction 

 illustrated in toad (Kampmeier, '25, fig. 13) are distended 

 sacs like those in figure 12, whether in gaps of the plexus or 

 terminal vessels at the periphery; a condition quite unlike 



