162 OTTO FREDERIC KAMPMEIER 



gathered in the marshes of the Isar near Munich and prepared 

 in Professor Rtickert's laboratory at the Anatomical Institute. 

 The specific descriptions in the following pages are based entirely 

 upon the specimens secured in Europe and, strictly speaking, 

 pertain only to them. The serial sections of the native toad were 

 not used extensively because they were prepared first, that is, 

 at a time when the writer's practice in making perfect series of 

 yolk-laden Amphibian larvae was still in its trial and error phase. 

 Such experimentation, particularly in regard to fixation, embed- 

 ding and sectioning, was conducive of better results with the 

 second batch of specimens, which were procured last spring^ 

 while the writer was engaged in study abroad. Mention of the 

 methods of technic as well as a review of the work of other in- 

 vestigators relating to the formation and growth of lymphatics 

 in Amphibia will be reserved for the later article. Bufo em- 

 bryos were chosen in preference to frog embryos because their 

 mesenchyme appears less scanty and less loose in texture, a 

 condition which it was supposed might prove helpful in distin- 

 guishing between lymphatic anlagen and tissue spaces. Never- 

 theless, it will become evident presently that such a precaution 

 was needless. 



At the beginhing of the inquiry the gaining of exact special 

 information was beset with what at first seemed a very discon- 

 certing obstacle, namely, the enormous number of yolk spherules 

 which are closely massed in all tissues of the young larvae and 

 cover and obscure everything except darkly staining cell nuclei. 

 The effort required to follow the development of such material 

 with some degree of accuracy exceeds the ingenuity and patience 

 expended in the preparation of satisfactory serial sections. Many 

 details of the earliest genetic changes cannot be followed with 

 certainty until much of the yolk has vanished. But in this 

 respect a comparison of young and somewhat older stages will 

 yield the important fact that the yolk does not disappear uni- 

 formly from the embryonic body. In other words, the period 

 in which the yolk substance is lost is different for the various 



''April and May, 1913. The manuscript was completed in the spring of 1914. 



