130 EDWARD L. RICE 
A careful study of the sections indicates clearly that the num- 
ber of hypoglossus nerve roots (as marked by independent emer- 
gence from the surface of the brain) is more than three. The 
thickness of my sections makes it unsafe to affirm that all such 
roots have been identified; the numbers must therefore be taken 
as minimal. In stage 4 five such origins have been recognized 
on each side. In general the conditions seem to be much more 
uniform in the region of the posterior foramen, where a single 
large root (made up of two subdivisions in stage 4) emerges; 
further forward the three or four nerve roots may leave the skull 
through two distinct openings or may be collected into a single 
foramen. In cases where only one anterior foramen is present, 
this foramen sometimes shows very clear evidence of its com- 
posite character in the fact that its extreme nerve roots, either 
anterior or posterior, run for some distance either in an open 
groove on the surface of the cartilage, or even in a closed canal 
in its mass, prior to entering the actual foramen. The variation 
in the number of the hypoglossus foramina in different stages is 
in no way related, in Eumeces, to the age of the embryo. The 
unquestionable bilateral asymmetry in certain embryos is strik- 
ing. Apparently the variations find their chief significance as a 
conspicuous warning of the danger of general conclusions based — 
upon single specimens. They may also be interpreted as an evi- 
dence of a generally distributed ability to form cartilage in situ 
in any part of the ‘membranous skull,’ as maintained by Gaupp 
(93, ’00), rather than by outgrowth from a comparatively few 
definitely localized centers. 
The following tabulation illustrates the range of variation 
observed in the Reptilia. Apparent contradictions are doubtless 
due in most cases to specific differences or to individual varia- 
tions, either dependent upon age or seemingly accidental as in 
Eumeces. The noticeable tendency of the earlier authors to 
record the smaller numbers suggests that faulty material and 
less exact methods have contributed to the confusion. Several 
of the records, notably of Siebenrock, are based upon figures, 
without confirmatory statement in the text. Bilateral asym- 
