178 OTTO FREDERIC KAMPMEIER 



the establishment of continuity. The writer would show figures 

 portraying these phases, but the number of illustrations already 

 far exceeds his intentions; moreover, such conditions are con- 

 cerned more especially with their later development and will 

 receive consideration in the subsequent contribution. At that 

 time the profuse plexus or network will also be considered which 

 in 8 and 9 mm. embryos is developed between the two lateral 

 lymph ducts and from which ultimately the definitive lateral 

 subcutaneous lymph vessels of the trunk are, so to speak, 

 crystallized. 



The history of science, in fact the history of lymphatic re- 

 search alone, has so often shown the fallacy of theorizing from 

 insufficient or problematical data and premises, that the writer 

 feels little inclination to base upon a simple finding an hypothesis 

 that shall attempt to harmonize or properly valuate the work 

 of other investigators at variance with his own. Only after 

 observation has been corroborated repeatedly or from several 

 viewpoints and the demonstration of fact is final can a law be 

 formulated which is sound, comprehensive and stripped of all 

 opinions and prejudices. Suggestions thrown out, however, to 

 give direction to inquiry are ever seasonable and little hesitation 

 is felt in expressing poignant ones. The purpose, then, of the 

 theoretical considerations in the following paragraphs is neither 

 to defend nor to refute any one view of lymphatic development; 

 nor is it the aim to effect a compromise between conflicting views 

 or to promulgate a new one. Consistent with the conditions in 

 Bufo, such considerations are offered as plausible possibilities, 

 the truth or error of which subsequent researches on other verte- 

 brate embryos will determine. 



If the interpretation of the structures described in this treatise 

 is the onl}" possible one as the author believes it to be; if the 

 lymphatic S3^stem of Amphibia is homologous to that of other 

 vertebrate animals as we expect it to be ; and if the morphological 

 dogma; like structure, like origin, is infallible, as all biologists 

 tacitly assume it to be, then the view of the direct mesenchymal 

 origin of lymphatics seems to be untenable But not only is this 

 theory affected; the opposing one also must certainly be radicalh' 



