PH0LADID2E. 
387 
s ; sometimes it is quite plain. On the upper edge of tlie anterior 
^ uncature of the body of tlie animal is the mouth, a sort of funnel, flat 
a nd slightly hell-shaped, furnished with four labial palpi, a stomach 
Without any peculiar feature, and a well-developed intestine. 
The heart consists of two auricles and a ventricle, which beat at 
Very irregular intervals, four or five in the minute. The blood is 
colourless, transparent, and charged with small irregular corpuscles, 
^he art of breathing is accomplished in the branchiae, or gills, and 
Mantle. Nevertheless the one half of the blood returns to the heart 
Without passing through these branchi®. 
The nervous system is well developed, and consists of a brain, 
Nervous filaments, and of ganglions, which are distributed in the 
Mantle, the branchi®, and the syphon tubes. 
The adult animal is surrounded by a sort of sheath, consisting of a 
8 °lid mucus, which has sometimes been described erroneously as form- 
! r 'o part of the animal. The Teredo, shut up in this tube, is limited 
1,1 its movements ; when observed in a vase, its motions are slow and 
^liberate — movements of extension and contraction, by tbe aid of 
"'V'h it contrives with difficulty to change its place; but nothing 
lu dicates a true creeping movement. In a state of nature, according 
0 -M. Quatrefages, the body of the animal is stretched out to three 
Ull >es its length without diminishing in any respect its proportional 
Sickness ; the afflux of water penetrating under the mantle, and of 
blood which accumulates in the interior vessels, sufficiently ae- 
rating for a phenomenon which at the first glance is very singular, 
j The Teredo deposits a spherical greenish-yellow egg. Shortly after 
relation, these eggs are transformed into larv®. At first naked 
^ Motionless, these larv® are soon covered with vibratile oils, when 
^y begin to move, at first by a revolving pirouette, afterwards 
jamming about freely in the water. When one of these larv® has 
0l md a piece of submerged wood, without which it probably could 
^ live, the curious spectacle is observed of a being which lubricates, 
e P by step, and as it requires them, the organs necessary for the 
p ovmance of its functions. It begins by creeping along the surface 
the wood by means of the very long feet with which it is furnished. 
^ 611 it is observed from time to time to open and shut the valves of 
!^ 6 little embryo shell which partly envelopes it. As soon as it has 
und 
a part of the wood sufficiently soft and porous for its purpose, it 
2 c 2 
