492 BENNET M. ALLEN 
MATERIAL AND METHODS 
A very complete collection of tadpoles of Bufo lentiginosus 
gathered in Lawrence, Kansas, afforded all of the stages, from 
the first appearance of the hind-limb buds to the completion of 
metamorphosis. A number of specimens were fixed in Flem- 
ming’s fluid and others in bichromate acetic. Large quantities 
of Bufo material fixed in 5 per cent formalin were used for a 
study of the gross features of the development of the thyreoid 
gland. ‘These proved to be most valuable. 
I wish to express my grateful acknowledgment of facilities and 
assistance accorded me by the Department of Anatomy of the 
University of Illinois Medical School. The greater part of the 
sections and illustrations used in this work were made by their 
technicians and artists. A series of gross dissections of Bufo 
were made in our University of Kansas Zoological Laboratory. 
The sections were cut at a thickness of 104 and were for the 
most part stained with haematoxylin and eosin. In some cases 
Heidenhain’s iron alum-haematoxylin was used. 
The dissections were made under a binocular microscope in 
such a fashion that the exposed thyreoid glands were left adher- 
ent to the hyoid cartilage, the whole being stained with alum- 
cochineal. These dissections were dehydrated and then cleared 
in oil of wintergreen. They were preserved and finally studied 
in this fluid. 
Measurements were made by means of a micrometer eyepiece, 
the maximum length, breadth, and thickness being determined 
in each case. In making a measurement of the thickness, the 
hyoid cartilage was held vertical between two small pieces of 
glass and the extreme thickness was measured in optical section. 
The accompanying table 1 gives the measurements obtained from 
a study of the dissections just mentioned. Length, breadth, and 
thickness of the gland were multiplied together to give a rough 
approximation of the volume, in effect the volume of a paral- 
lelopiped that would contain the gland. The latter is flattened 
oval, somewhat irregular in some instances, but for the most 
part of relatively constant shape. 
