334 ROY L. MOODIE 
5. The nature of the influence of the lateral-line canals on the _ 
formation of the peripheral osseous elements is found to be me- 
chanical because it furnishes an inactive substance in the form 
of the dense connective tissue of which the canals are composed. 
They furnish a more highly organized basis of colloidal material 
for the attraction of lime deposition on account of their preco- 
cious development and because of the mechanical influence of 
the surface and capillary features present on the surfaces of the 
canals. 
6. The earliest spicules are laid down parallel to the canals. 
They are wavy in outline and irregular, the irregularity being 
due to a response to the form of the irregularly placed osteoblasts 
between which the threads are deposited. The threads are 
granular and non-crystalline. 
7. The suborbital chain of bones, between the segments of 
which appear the tubules, is not completed until after the 50 mm. 
stage. 
8. The histological features of the canals and associated bones 
bear out the interpretation given to the appearances in the 
cleared specimens. This is shown by the intimate association 
of the spicules of bone to the walls of the canals. The thickness 
of bone is increased at the expense of the canals, from without 
inward. 
9. The application of these determined embryological facts 
to paleontology is considered justifiable because of the con- 
stancy of structure in the fishes and amphibians. The tubular 
lateral-line canals are there before bone develops. They are in 
the way and introduce disturbing factors of a mechanical nature 
to which the peripheral osseous elements in their formation must 
respond. 
