124 MARION HINES 
The only deduction which the present series allows is that the 
growth in this region is immaterial. In sucha case this measure- 
ment lends another landmark to the study of the midline. Prob- 
ably the most striking group of figures presented are those of the 
paraphyseal arch. There is little change in the antero-posterior 
length; in this particular series, the younger embryos possess 
the longer arches. The shortening of the distance between the 
Fig.7 Medial sagittal view of a model of a 11.8-mm. embryo belonging to the 
Mall Collection in Baltimore, no. 1121. X 16}. 
anterior and the posterior limb coincides with the decrease in 
width and the formation of the actual plexus itself. The con- 
stant feature is not the pouch; it is rather the simple arch itself. 
If these figures are substantiated by subsequent work, the para- 
physeal arch will be a more prominent feature of the younger 
stages than of the older ones. This finding seems to place the 
human embryo in phylogenetic line with other mammals, the 
difference being not in its relative extent, but in the complexity 
of its bizarre outpouchings. This does not disagree with the work 
