William Abbott Herdman

“ The anus opens into the dorsal part of the peribranchial cavity near to the atrial aperture. The walls of the stomach are glandular; and a system of delicate tubules with dilated ends, which ramifies over the outer wall of the intestine and communicates with the cavity of the stomach by means of a duct, is probably a digestive gland. ”

“ In the tail part of the embryo the neural canal remains as a narrow tube, while the remains of the wall of the archenteron the dorsal part of which becomes the notochord are converted into lateral muscle bands (fig. 10, G) and a ventral cord of cells, which eventually breaks up to form blood corpuscles. As the tail grows longer, it becomes bent round the trunk of the embryo inside the egg-membrane. About this period the epiblast cells begin to form the test as a cuticular deposit upon their outer surface. ”

“ The buds while still very young migrate from their place of origin on the stolon, divide by fission, and become attached to the dorsal outgrowth of the body of the nurse, where they develop. The three forms produced are as follows. (1) Nutritive forms (trophozooids) , which remain permanently at tached to the nurse and serve to provide it with food; they have the body elongated dorso - ventrally, and the musculature is very slightly developed. ”

“ It may either be stretched out so as to extend for some distance anteriorly, or as is more usual be concentrated to form along with the reproductive organs a rounded opaque mass near the posterior end of the body, known as the visceral mass or "nucleus." The embryonic development is direct, no tailed larva being formed. ”

“ The colony gradually increases by the formation of buds from these four original ascidiozooids. PHYLOGENY. The accompanying diagram shows graphically the probable Phyloorigin and course of evolution of the various groups of Tunicata, geny. and therefore exhibits their relations to one another much more correctly than any system of linear classification can do. The ancestral Proto- Tunicata are here regarded 1 as an offshoot from the Proto-Chordata the common ancestors of the Tunicata (Urochorda) , Amphioxus (Cephalochorda) , and the Vertebrata. ”

“ E. Embryo showing body and tail and completely formed neural canal. F. Larva just hatched; end of tail cut off. G. Transverse section of tail of larva.
adp, adhering papillæ of larva; at, epiblastic (atrial) involution; au, auditory organ of larva; ar, archenteron; bc, blastocœle; bp, blastopore; ch, notochord; ep, epiblast; hy, hypoblast; nc, neural canal; nec, neurenteric canal; oc, ocular organ of larva; g, gelatinous investment of embryo; m, muscle cells of tail; mes, mesenteron; mc, mesoderm cells; nv, cerebral vesicle at anterior end of neural canal. ”

“ At a somewhat later stage a number of cells placed at the posterior end of the body alongside the future nucleus become filled up with oil-globules to form a mass of nutrient material the elseoblast which is used up later on in the develop ment. ”

“ This species is found in most of the European seas, generally in shallow water on a muddy bottom. External characters.It has an irregularly ovate form, and is of a dull grey colour. It is attached to some foreign object by one end (fig. 1 ) . ”

“ They possess the power to form Strucwith great rapidity an enormously large investing gelatinous layer ttire of (fig. 11) , which corresponds to the test of other groups. This was Appenp,p n.y, dicularia. Fio. 12. Semi-diagrammatic view of Appendicularia from the right, a, anus; at, one of the atrial apertures; app, tail; br, branchial aperture; brs, branchial sac; ”

“ The test is well developed and ^ stolon; m, muscle band of the i, i, .1 L f /. mantle. (Uncmal.) adheres closely to the surface 01 the mantle. The muscle bands of the mantle do not completely encircle the . em j, body. Theyare 5 present dorsally and laterally, but the major ity do not reach the ventral sur face. In many cases neigh bouring bands join in the med ian dorsal line, Pro 16 _ genii-diagrammatic representation of Salpa from (ng. 14) . Ihe leftside. Lettering as before; emb, embryo; m, mantle; anterior end of I, languet; sgd, duct of subneural gland ”