ALLMAN, ON APPENDICULARIA. 87 
that these naturalists had never got a sight of so remarkable 
an object, for I soon found that it required the greatest 
possible care to prevent its detaching itself; and that, even 
with every precaution, it remained but a very short time after 
capture in connexion with the body of the Appendicularia. 
The irritation caused by transferring the contents of the 
basin into a glass jar for more effective examination caused, 
in most cases, its separation, and it was only in very few 
instances that Isueceeded in bringing home a perfect specimen. 
Even then I had generally the mortification of seeing the active 
Appendicularia break away from its “haus” almost imme- 
diately after arrival ; and when it is further borne in mind 
that the separation of this appendage is almost instantly 
followed bv its collapse, and by the consequent losing of all 
its most striking characters, the difficulty attending its exami- 
nation will be easily conceived. 
To transfer the animal in a perfect state into a small 
trough for investigation under the compound microscope was 
impossible, and I was therefore obliged to keep it in a large- 
sized glass jar, and content myself with such observations as 
a simple hand-lens would enable me to make. 
A correct idea of the “haus” of the present species of 
Appendicularia may perhaps be best obtaimed by imagining 
a clear gelatinous oviform body, which in full-sized specimens 
has its greaterdiameter about five lines inlengthand its smaller 
about four (Plate VI). That plane of the greater diameter 
which passes vertically through the body of the animal will 
divide the “ haus” into a right and a left half, and the 
common plane of any two lesser diameters will divide it into 
an anterior and posterior half. 
Within the gelatinous mass, and chiefly occupying the 
anterior half, are two remarkable structures, each shaped lke 
a double fan, whose general form may be best understood by 
imagining a semicircular membranous lamina to be folded 
upon itself along a line uniting the middle points of its 
curved and straight margins. There will thus be formed a 
double fan, constructed of two single fans, united along one 
edge, but open along the other two. The two double fans 
thus constituted are situated symmetrically in the gelatinous 
mass, to the right and left of its greater diameter, their bases 
or convex edges being directed towards its surface, and their 
apices nearly meeting one another at a point in the greater 
diameter a little in front of the centre, while their axes (a 
line drawn from the apex to the centre of the base) will he 
nearly in the horizontal plane passing through the greater 
diameter. The closed edge is directed forwards and inwards, 
