264. DR. H. W. MARETT TIMS ON 
Writing in ‘ Nature’ [11], referring to these vestigial teeth, 
Huxley pointed out that “it would be interesting to examine 
foetal guinea-pigs in relation to this point; at present they are 
known to possess only the hindermost deciduous molars, so far 
agreeing with the marsupials.” Freund [10] has also discovered 
the existence of vestigial milk-incisors in the squirrel in both jaws. 
Though he inclines to the belief that these vestiges are to be 
interpreted in this manner, yet he implies the existence of some 
doubt. From his description of the connection between the neck 
of the permanent teeth and that of the vestigial teeth, and 
from the fact that the rudimentary enamel-germ and the large 
incisor are included in the same thickened connective-tissue 
capsule, I think there can be little doubt but that they are 
vestigial milk-incisors, and that Freund, as Woodward says, is 
* over-cautious and inclined to underestimate the facts which 
suggest that condition.”” Again, Mr. M. F. Woodward (J. c.) has: 
described in the mouse “a pair of very minute calcified tooth- 
rudiments in connection with the two large upper incisors, one 
each side of the jaw.” These rudiments he considers to represent 
‘€ the last stage in the reduction of a vanishing tooth, the earlier 
stages of which are to be seen in the rabbit and squirrel.” The 
guinea-pig will thus be seen to add a still further stage in the 
degeneration of this tooth, forming a very complete and inter- 
esting series. 
Two observers, Freund [10] and Adloff [1], have also examined 
specimens of Cavia at this stage; their measurements differ 
considerably from my own, and possibly the discrepancy may 
be due to the method of measuring: as I estimated the length 
from the tip of the snout to the root of the tail circumfer- 
entially, this would obviously give a greater length than if 
measured in a straight line. Freund has also examined two 
younger stages, the earlier one having a cephalic length of 
45 mm., the measurement of the other not being given. This 
writer gives but few details as to the condition found in these 
three young stages, merely stating that he found no trace of a 
germ for the second incisor, and nothing in the diastema beyond 
a few thickened cones of epithelium, which he could not satisfy 
himself were to be regarded as tooth-rudiments. Adloff, on the 
other hand, gives more details of the examination of his speci- 
mens at this stage, and accompanies his description by three 
figures. His description of the tooth which he identifies as Pd.3 
