Chapter V: The Evidence of the Thyroid Gland

The value of the appendage-unit in non-branchial segments--The double
nature of the hyoid segment--Its branchial part--Its thyroid part--
The double nature of the opercular appendage--Its branchial part--Its
genital part--Unique character of the thyroid gland of Ammocoetes--
Its structure--Its openings--The nature of the thyroid segment--The
uterus of the scorpion--Its glands--Comparison with the thyroid
gland of Ammocoetes--Cephalic generative glands of Limulus--
Interpretation of glandular tissue filling up the brain-case of
Ammocoetes--Function of thyroid gland--Relation of thyroid gland
to sexual functions--Summary 185