The pointing out of this great fact has seemed to us a useful addition to the great law of evolution. It supplements it; it gives a reason why.
Could he who first saw these points have read these final pages, it would have lightened the responsibility of the one upon whom the completion of the work has fallen. But he died when the work was nearly finished. The investigation is of necessity incomplete, but nothing bears such misstatements as truth, and though specialists may demur to certain points, the fundamental arguments will probably remain intact.
- Acetabula. Lat. acetabulum, a little vessel. Sucking discs as on the tentacles of Physalia.
- Aorta. Gr. The chief artery.
- Cephalothorax. Gr. kephale, head; thorax, chest. The anterior division of the body in Crustacea and Arachnida, composed of the amalgamated segments of the head and thorax.
- Cilia. Lat. cilium, an eyelash. Microscopic filaments having the power of vibratory movement.
- Cœnosarc. Gr. Koinos, common; sarx, flesh. The common stem uniting the separate animals of compound hydrozoa, &c.
- Corpuscle. Lat. corpusculum, a little body. Small coloured bodies, as in the endoderm of hydra, [p. 59].
- Differentiated. Modified into definite organs, or parts; as distinct from structureless protoplasm.
- Ectoderm. Gr. ektos, outside; derma, skin. The internal layer or skin of the Cœlenterata.
- Efferent. Lat. effero, to carry out. A vessel which carries fluids out of the body is said to be efferent.
- Endoderm. Gr. endon, within; derma, skin. The inner layer or skin of Cœlenterata. See [Ectoderm].
- Endosarc. Gr. endon, within; sarx, flesh. The inner layer of sponges.
- Epidermal. Gr. epi, upon; derma, skin. Relating to the outer layer of skin. As applied to colour, surface pigment as distinct from hypodermal, or deep-seated colour.
- Gastrovascular Canal. Gr. gaster, belly; Lat. vasculum, a little vessel. The canals or vessels in the umbrella (manubrium) of hydrozoa.
- Gonidia. Gr. gonos, offspring; oidos, like. Reproductive bodies in Sea-anemones.
- Hydranth. Gr. hudor, water; anthos, flower. The bodies or polypes of hydroids which exercise nutritive functions. They were called polypites by Huxley.
- Hydrophyllia. Gr. hudor and phyllon, a leaf. Leaf-like organs protecting the polypites of hydrozoa.
- Hydrosoma. Gr. hudor and soma, body. The entire organism of a hydrozöon.
- Hypodermal. Gr. hypo, beneath; derma, skin. In colour, such as lies beneath the surface, as distinct from epidermal.
- Lythocysts. Gr. lythos, stone, kystis, a bladder. Sense organs in hydroids, consisting of transparent capsules inclosing round transparent concretions.
- Manubrium. Lat. a handle. The central polypite suspended from the interior of the umbrella of hydroids.
- Mesoderm. Gr. mesos, intermediate; derma, skin. The middle layer of sponges, &c.
- Mesothorax. Gr. mesos and thorax. The middle division of the thorax in insects, carrying the second pair of legs.
- Peristome. Gr. peri, about; stoma, a mouth. The area surrounding the mouth in sea-anemones.
- Pneumatocyst. Gr. pneuma, air; kystis a bladder. The air-sac contained in the pneumatophore, see below.
- Pneumatophore. Gr. pneuma; phero, to carry. The float of certain hydrozoa (Physophoridæ.)
- Polypite. Gr. polus, many; pous, foot. The separate animal or zöoid of a hydrozöon. See [Hydranth].
- Protoplasm. Gr. protos, first; plasso, I mould. The jelly-like matter which forms the basis of all tissues. It is identical with the sarcode or flesh of protozoa.
- Sac. Lat. saccus, a bag, a small cell.
- Sarcode. Gr. sarx, flesh; eidos, form. The protoplasm of protozoa, &c., which see.
- Spadix. Lat. spadix, a broken palm branch. In zoology a hollow process occupying the axis of the generative buds of hydrozoa.
- Sporosac. Gr. spora, a seed, and sac. The body containing the ova of hydrozoa.
- Somatic Fluid. Gr. soma, the body. The fluid which contains digested food, and taking the place of blood, circulates through the body of hydrozoa.
- Tentacles. Lat. tentaculus, a little arm. The arms or prehensile organs of Sea-anemones, &c.
- Thread Cells. Cells containing an extensible microscopic thread, possessing stinging properties, common among the Cœlenterata.
- Thorax. Gr. a breastplate. The chest.
