474 
TRANSFORMATIONS OF INSECTS. 
skin of the sac. By this arrangement the eggs are placed between 
new and inner and old and outer integuments, and as the retaining 
structures are cast during the moults which the perfect Cirripede 
undergoes, the ova are then liable to be set free. The moults 
are restricted to the outside of the membranes, uniting the valves 
of the shell in the young adult form, and to the lid-membrane in 
the sessile Balani. In the others the surface of the peduncle dis- 
integrates, and is removed, and the scales upon it are served in the 
same manner, and the delicate membrane lining the sac and the 
skin of the whole body are regularly shed, and also the membranes 
of the mouth, oesophagus, and the horny jaws. The new spines of 
the cirri are formed within the old ones. The growth of these 
creatures is often very rapid, and the skin sheddings numerous, 
on account of their being necessary for the enlargement of the 
body and the expansion of the shell. 
The pedunculated Cirripedia are found in nearly every sea, 
and are fixed to stationary and fioating objects. Some are 
attached to the shells of Mollusca which live on the shore, and 
others to timber and weed, but a great many live fixed upon 
and even partly within the skin of whales and sharks. In these 
last instances the peduncle is sunk into the skin of the large 
marine creatures, and the cement glands produce the adhesion. 
The range of the sessile barnacles is immense, and they frequent 
coral reefs and all shores where there is rock and clear water 
free from much mud and sand. Some frequent turtles, sea snakes, 
others Crustacea , whales, manatees, and shells. 
Before 1835 Mr. Vaughan Thompson discovered the larva 
when about to become metamorphosed into a barnacle, and 
Burmeister recognised that the larval condition was divided into 
two stages, the early and later creatures being as different from 
each other as they both are from the mature Cirripede. Goodsir 
drew the larva of Balanus in the first stage, and Spence Bate 
has made observations and drawings of those of several species. 
The following description of the larvae and of their metamorphoses 
is abstracted from Charles Darwin’s monograph (Ray Society). 
The ova of the Lepadidce (pedunculated Cirripedes) are hatched 
whilst within the sac of the parent, and the young larva of the first 
stage is nearly globular in shape (in Scalpellum vulgarc , an English 
