EXPLANATION OF THE PLATES, 
The figures were copied from my pencil drawings with the exception of Piates II, 
and VII. , which I drew on stone from the specimens. 
Plates L, III.-VL, VIII.-XIIL, XVI., XIX., XX., XXII., XXVI., XXXII.-XXXVIL, 
XXXIX.-XLIL, and XLIX. were lithographed and printed by Dobb & Co., Liverpool; 
while plates XIV., XV., XVII., XVIIL, XXL, XXIII.-XXV., XXVII.-XXXL, 
XXXVIIL, and XLIII.-XLVUI. were lithographed and printed by Mr. F. Huth, 
Edinburgh. 
It should be stated that some of the anatomical figures {e.g., some of those repre- 
senting the structure of the Ascidiozooids, and some of the branchial sacs) are “ combina- 
tion figures,” formed of portions drawn from several different specimens and pieced 
together. 
The following powers were used in drawing the figures for the plates : — 
S. 1 = Swift’s 1 inch objective, magnifying about 50 diameters. 
S.|= ,, d » 2.30 „ 
» I" » ,) 330 „ 
Z.jn = Zeiss’ A objective (oil immersion), magnifying about 950 diameters. 
LIST OF THE ABBREVIATIONS. 
a. 
Anus. 
br.f. 
. Longitudinal folds in branchial sac. 
ab, ahd. , 
Abdomen of Ascidiozooid. 
br.l. 
. Branchial lobe. 
ad. . 
Adhering appendage. 
hr.n. 
. Nerves arising from branchial end 
ap. . 
Appendage from body of Ascidiozooid. 
ganglion. 
at. . 
Atrial aperture. 
br.s. 
. Branchial sac. 
at.l. 
Atrial languet. 
b.v. 
. Blood-vessel. 
at.n. 
Nerves arising from atrial end of ganglion. 
coe. . 
. Caecum of stomach. 
at.tn. 
Atrial tentacles. 
c.d. 
. Connective duct in the branchial sac. 
h.c. . 
Blood-corpuscles. 
cl. . 
. Cloacal aperture. 
bl. . 
Bladder cells in test. 
d.l.. 
Dorsal lamina. 
hr. . 
Branchial aperture. 
d.t. . 
Dorsal tubercle. 
