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I must preface this with a few words upon the homology of the roots of the Rhizocephala, i.e. the tubules which penetrate from its point of adhesion into the body of the host, ramify amongst the viscera of the latter, and terminate in caecal branchlets. I have therefore supposed these appendages to be the rudiments of the future roots.
But in many other instances I have failed to detect any such indication, even with much higher powers. The small ramifying tubules might at first sight be taken for some traces of a vegetable tissue, but my colleague, Dr. Scott, assures me that they do not in the least resemble any tissue found in the bamboo. I have myself no doubt that it is an inorganic structure.
It is not improbably analogous to the peculiar ramifying tubules formed in a solution of water glass when a crystal of copper sulphate is suspended in it, as shown by Dr. Brit. Similar forms also occur on a larger scale in some agates, and the artificial cells of Traube may probably be regarded as analogous phenomena.
In one part of this organ the tubules were larger than elsewhere, and one of them exhibited spermatogenesis in progress. The left and larger gonad had a quite similar structure, but at its lower end were found two ova enclosed within a follicular epithelium.
The ovaries are analogous to the testicles of the male. Their function is to secrete ova. Leading from the ovaries, but connected with the surface of these glands only during the period of oestrum or heat, are the fallopian tubules. Their function is to carry the ovum from the ovaries to the uterus.
Later on the hairs and the sebaceous glands entirely disappear, and the milk gland alone is left with its tubules and ducts opening into the cavity of the teat.
The milk tubules from the different portions of the gland converge and form larger tubules that finally empty into small sinuses or reservoirs at the base of the teat. Leading from these sinuses are one or several milk ducts that open at the summit of the teat. The testicles are the glandular organs that secrete the spermatozoa, the essential elements of the seminal fluid.
*Urea* is the most abundant solid constituent of the urine and is the chief waste product arising from the oxidation of nitrogenous substances in the body. Although secreted by the cells lining the uriniferous tubules, it is not formed in the kidneys. The secreting cells simply separate it from the blood where it already exists.
The follicles of these hairs extend down into the derma, and from the upper end of the follicle, i.e. near the aperture of the invagination, a long cellular outgrowth extends down into the derma, branches at its end, and becomes hollow. These branches are the tubules of the future milk gland. Another outgrowth from the follicle forms a sebaceous gland.
Branch from renal vein. 3. Small artery branches, one of which enters a Malpighian capsule . 6. Small vein leaving the capsule and branching into the capillaries which surround the uriniferous tubules. 4. Small veins which receive blood from the second set of capillaries. 8. Tubule showing lining of secreting cells.
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