Fam. I. Salpidae.—Colonies as chains. Intestine in a sinistral loop, or if elongated (Ritteriella), produced backwards. (i.) In testinal hernia moderate. Marginal bands of endostyle sym metrical (Traustedtia?).
—Traustedtia, with radiating appendages in OZ; Pegea, 4 endostyle deep.
Sub-fam. ii. Iasinae :—M separate, but incomplete dorsally in OZ, embryos 3-5, endostyle shallow, the accessory gland tract reduced or obsolete. Iasis, 1-, no tails, Thetys, , tails in OZ.
(ii.) Intestinal hernia inconspicuous or absent. Marginal bands asymmetrical, the left vestigial or absent.
Sub-fam. iii. Thaliinae.—M usually grouped (3-4) in front and separate (2-5) behind, especially in OZ, sometimes complete ventrally. Thalia, tails in OZ; Salpa, BZ with paired pointed processes in front and behind; Ihlea, all M in OZ complete ventrally.
Incertae sedis.—Ritteriella, M connected dorsally by a long anastomosis, intestine loosely coiled and protruding, or in OZ produced backward beneath extended cloaca; Brooksia, I, with ventral muscular proboscis in OZ.
Fam. II. Cyclosalpidae.—Colonies as wheels (except C. vir gula). Intestine in OZ extended forward above the gill. Endo style with interlocking lips, left marginal band obsolete.
Cyclosalpa, M highly variable, intestinal hernia in BZ enormous, except C. pinnata in which the intestine extends for ward below the endostyle ! Usually phosphorescent.
Order III. COPELATA ( = Larvacea) This order is characterised by small pelagic forms with one pair of tubular gill-slits (spiracles), reduced endostyle, and a horizontal tail bent forwards beneath the body. Cloaca absent, represented behind by a large, thin-walled tunic-free area which includes the apertures of intestine, spiracles, and gonads (genito spiracular area). Test differentiated and expanded as a filtering mechanism (the house), formed by thickened ectoderm of the pregenital region (oikoplastic epithelium). From its boundary frequently arises a transverse dorso-lateral fold, directed for wards (dorsal hood or veil). Intestine normally coiled to right
of oesophagus. No budding, but epicardial vestiges possibly represented by the pharyngeal packets of Fritillaria (and oral glands of Oikopleura?). The minute structure of the body is characterised by great economy of cellular elements.
(As elaborations of the test in Appendicularians replace in bio nomical value the internal modifications of other Tunicates, a phyletic classification of Copelata should rest largely upon the structure of the house, but various uncertainties prevent us from making use of more than a few conspicuous features. Fol's account of the house of APPendicularia [5874] seems to have been misunderstood by Lohmann, who has nevertheless made valuable observations on the house-rudiment [1896, 1899]. This genus is regarded by the present writer, in agreement with its discoverer, as the most central and primitive type of the Cope lata. The classification adopted differs accordingly in various respects from Lohmann and Biickman's recent revision [1926]).
(N.B. The terms anterior, posterior, etc., when applied to the house, are here used in their usual morphological sense, and not with reference to the direction of locomotion, as used by Lohmann. For brevity oikothelium is used for oikoplastic epithelium.) Suborder I. ENDOSTYLOPHORA (Garstang, 1895). Pharynx with endostyle. House bilaterally symmetrical, with separate inhalant and exhalant apertures.
Fam. I. Appendicularidae.—Intestine tubular, to right of stom ach. Rectum ventral, directed forwards. Endostyle an open groove with an anterior tuft of cirri. House enclosing the body, with an anterior (oral) aperture, a paired filtering mechanism above, and a caudal chamber below.
Sub-fam. i. Appendicularinae.—Anus behind spiracles, to right of tail-base. Oesophagus ventral. Oikothelium broad and long, giving rise to two dissimilar pairs of fibrillated membranes Dor sal hood arising far back. House not much expanded, taller and broader than long, caudal chamber vertical (with postero-ventral aperture?), tail pointing downwards.