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XIII. On the Anatomy of the Genus Appendicularia, with the Description of a new Form, 
By Epwarp L. Moss, M.D., Assistant-Surgeon, R.N., H.M.S. Simoom. | Communi- 
cated by Professor HUXLEY, F.L.S. | 
(Plate XLVII.) 
Read December 3rd, 1868, 
THE structure and habits of Appendicularia have for some time attracted the attention 
of biologists both at home and abroad ; but few new facts bearing upon its anatomy have 
been added to English science since the observations of Professor Huxley, in the Philo- 
sophical Transactions of 1851. 
My attention was first directed to these interesting little animals by the capture of a 
single specimen between Gibraltar and Malta; and the paper just alluded to was found of 
the greatest assistance in deciphering the particulars of its anatomy. As many specimens 
have since been from time to time obtained, some fresh points worthy of notice have pre- 
sented themselves. The disjointed character of the following remarks must be accounted 
for by the peculiar difficulties of study at sea, the minute size and transparency of the 
 Appendicularice, their extreme activity while alive, and the almost instantaneous disor- 
ganization of their delicate tissues in the moment of death.. An average specimen care- 
fully removed from a glass of sea-water, by the aid of a pipette, and placed in a cell a 
quarter of an inch wide and a line deep, will live about ten minutes. The rapid vertical 
undulations of its appendix, only intermitting for an instant, until the shrivelling of ¡ts 
external tunic, and occasionally the exfoliation of a layer of the same tunic from the 
body, immediately precede dissolution. _ 
The forms of Appendicularia which have come under my notice may be conveniently 
divided into the short- and the long-bodied, which seem respectively to represent the 
Branchial and Intestinal groups of compound Tunicaries. The former presents an ellip- 
tieally shaped body, especially when surrounded by an unshrunken external tunic, and an 
appendix formed on the plan common to all Appendicularie, but slightly varying in out- 
line in different specimens, attached hæmally with its plane horizontal to that of the 
body. 
"is Atlantic and Mediterranean members of this group, which includes the .4. copho- 
cerca and A. cerulescens of Gegenbaur, as well as the new form described below, vary in 
length from the thirtieth to the third of an inch, and are therefore rather smaller than 
those described by Professor Huxley in the paper before referred to. The external tunic 
is always conspicuously developed; in some specimens it presents two tubular processes 
projecting from the body in the neighbourhood of the ciliated respiratory openings. 
When such processes exist, they, together with a delicate layer of the tunic, are invariably 
- ghed before the death of the animal. The posterior lip of the branchial orifice is occasion- 
© ally furnished with minute tentacula; and imbedded in the substance of the lip, a short 
