62 OTTO F. KAMPMEIER 
delineate the topography of the lymphatics functional in an 
intermediate stage. 
In Bufo tadpoles,* 12 to 15 mm. long, the chief lymph vessels 
are already laid down, so that we may say the second phase of 
lymphatie organization, suggested above, begins at this time. 
31 spent the spring and summer of 1913 with great profit and pleasure at the 
Anatomical Institute of the University of Munich, where, through the kindness 
of Professor Riickert, I was able to enjoy all the facilities of those delightful 
laboratories. I wish also to mention Dr. H. Marcus, who placed his series of 
larval Gymnophiona at my disposal. Further, I express my gratitude to Mr. 
Otto Balbach, of the University of Pittsburgh, who prepared the later series of 
my numerous sectioned anuran embryos. 
Toad embryos constitute by far the bulk of the material used in the investiga- 
tion. These specimens are of two species, the American common toad, Bufo 
lentiginosus, and the European, Bufo vulgaris (?), and are respectively from 
New Jersey and Wisconsin, and from the marshes along the Isar River near 
Munich. The writer neglected to determine with absolute certainty the specific 
name of the latter form before leaving Munich. There are but two species which 
can be considered, Bufo vulgaris and B. viridis, but after comparing them as to 
distribution, breeding habits, etc., as described in the standard works of Zoology, 
he is confident that it is Bufo vulgaris. The descriptions and figures are based 
mainly on the embryos of this European form which were gathered later in the 
course of the investigation when the writer had attained greater success in the 
preparation of tissues so profusely filled with yolk as are amphibian embryos. 
The ova of these Anura were collected shortly after laying and developed in the 
laboratory aquaria. To procure a closely graded ontogenetic series, active 
individuals were fixed and preserved at intervals of three to four hours. 
The ordinary methods of technique were employed in the preparation of the 
serial sections. Before the embryos exhibited movement, they were fixed directly 
in Zenker’s fluid, but later embryos were first anesthetized in a weak chloretone 
solution to prevent the distortion or tearing of the delicate tissues which might 
result from the writhing or twitching of the body when placed in the irritating 
fixative. The difficulties at first encountered in making satisfactory serial 
sections, apparently due to the brittleness of the yolk-laden tissues when xylol 
was used as the clearing reagent, were overcome by using cedar oil instead and 
by diminishing the time of paraffin infiltration to a minimum. Both the graphic 
method and the modified Born’s wax-plate process were enlisted in the execution 
of the reconstructions. In every case, the outline drawings of the sections were 
made with the Edinger projection apparatus. The writer also attempted to 
inject the vascular channels of a number of embryos, but on the whole he met with 
little success. The continuous layer of brown pigment in the skin of the toad 
larvae hides the underlying structures, and the cannula needle can therefore not 
be directed with the same degree of certainty as when transparent fish embryos 
or the much larger pig or chick embryos are injected under the binocular micro- 
scope. 
