GROWTH AND LIFE HISTORIES 75 



The antennules of the cypris larva are relatively large, and 

 project in front of the carapace; a cement gland opens on the third 

 segment and serves for attachment of the larva. Once attached 

 there are changes in the proportions of various parts of the body 

 (fig. 35). The thorax is bent back so that it comes to lie across the 

 longitudinal axis of the carapace. If the barnacle is one with a 

 stalk there is a great increase in length in the region in front of 

 the mouth, but the mouth has meanwhile been bent away from 

 the point of attachment. The thoracic legs become longer and beset 

 with fine hairs in readiness for the adoption of the adult method 



Fig. 35. Metamorphosis of a stalked barnacle. A, Cypris 

 attaching by means of its large antennule. B, reorientation 

 of the body within the carapace. C, growth of the pre- 

 oral region of head and assumption of adult form, (from 

 Calman s after Korschelt and Heider). 



of feeding (see p. 24). Calcareous plates are formed in the carapace; 

 the details of the arrangements of these plates varies from one 

 genus to another. In Lepas the carapace retains more or less the 

 cypris shape, while in stalkless barnacles the cypris carapace is lost 

 and a new carapace is developed to encircle the body. With the 

 development of calcareous plates the barnacle assumes its adult form 

 and spends the rest of its life attached to the place it selected as a 

 cypris. It is clear that the selection of a settling place by a cypris is 

 an important event in the life of a barnacle. Experiments have 

 shown that many species settle gregariously. A cypris prefers to 



