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 Cirripcde 

 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 Cirripcdia are found in nearly every sea, 

 and are fixed to stationary and floating objects. Some are 

 attached to the shells of Molliisca 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 Cirripcde. Goodsir 

 drew the larva of Balaniis in the first stage, and Spence Bate 

 has made observations and drawings of those of several species. 

 The following description of the larvaj and of their metamorphoses 

 is abstracted from Charles Darwin's monograph (Ray Society). 



The ova of the Lepadidcg (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 Scalpclhim viilgarc, an English 



