606 
Glimpses only have been gained of the presence of tonsils in other 
forms, namely: — lateral tonsils in Plethodon cinereus erythronotus, 
and Diemyctylus viridescens; a sublingual tonsil in Amblystoma 
punctatum. On the other hand, no trace of tonsils was to be found 
in a series through the head of an adult Gyronophilus porphyriticus. 
It should be said, however, that the examination was not made by 
means of series specially prepared for this study but in series already 
previously used in other work and hence these comparative obser- 
vations are quite fragmentary. 
The Toad. (Bufo lentiginosus.) The availability of numerous 
series in this form, before, during, and after metamorphosis, permitted 
a general examination as complete as in the case of Salamandra atra. 
The only tonsil of constant oceurrance and location is the sublingual 
tonsil. This, however, seems to be an absolutely constant structure. 
In young newly metamorphosed (11—15 mm) toads of which nine (9) 
were examined the sublingual tonsil was in every instance present 
on both sides and symmetrically placed. The region is quite charac- 
teristic. The tonsil (Figure 14) is located in the mucous membrane 
over the point where the ceratohyale and the manubrium corporis 
hyoidei join. Ventral to it is the ceratohyal lymph sinus with the 
Septum glosso-hyoideum upon its medial side. The relation of the 
lingual nerve, artery and vein is also marked. The vein passes directly 
beneath and medial to the tonsil receiving contributory vessels from 
the tonsil, the association of the vein with the tonsil being, as in the 
case of Salamandra, close but much more evident in Bufo. Somewhat 
tarther caudad the artery and nerve pass to the ventral side of the 
Processus alaris of the hyoid and the (parahyoid) lymph sinus, the 
vein continuing its course dorsally and superficially, immediately 
beneath the oral mucous membrane. 
In its development as in its morphology, the tonsil is constant. 
It appears after the arms have broken through in the period of rapid 
metamorphosis, at about the time when the tail is a mere stump. 
It is already established when the metamorphosis is finally completed, 
but it continues to grow for a period of time the limits of which have 
not been yet established. The complicated morphological changes 
that this region passes through during the development of the larva 
and its transformation have not been followed as yet in sufficient 
detail. The sublingual tonsil appears, however, as has been previously 
stated, at the cephalic end of the furrow (II) leading forward from the 
branchial chamber. 


