110 BALANIDiE. 



terior pairs of legs. I may here remark that in the pupa the 

 anterior natatory legs have become, like the others, biramous j 

 but yet, as it were for the purpose of showing their meta- 

 morphosis from the uniramous legs of the earlier stages, 

 they have their bristles arranged rather differently from 

 those on the succeeding five pairs of legs. 



Larva in the third or pupal stage. — I have given a lateral 

 view of the pupa of Lepas australis (PI. 30, fig. 2), illus- 

 trative of the description in my former volume ; the spe- 

 cimen is drawn as if transparent, and it was to a certain 

 extent thus rendered by boiling in caustic potash. A 

 sketch of the position of the young Cirripede within the 

 pupa, was made by the camera. At first the drawing will 

 perhaps hardly be comprehended : the darker shaded por- 

 tion to the left of the letter {])) shows the extent of the 

 sack, with the included thorax and natatory legs of the 

 pupa : to the right of the same letter, if we do not con- 

 sider the young included Cirripede, the only organs dis- 

 tinguishable in the mass of cellular and oily matter, are the 

 alimentary canal, the cement-glands {t), i. e. the incipient 

 ovaria, and the cement-ducts {t') which enter the antennae. 

 A view is also given (fig. 4) of the ventral surface of the 

 pupa ; and a transverse section (fig. 7) of the carapace, taken 

 close to the eye-apodemes. On comparison with the larva 

 in the second stage, the changes in external appearance and 

 structure are not very great ; the prehensile antennas are 

 freed from their cases ; the two eyes stand further apart ; 

 the three posterior pairs of legs have been developed, and 

 a small abdomen has become distinctly separated from the 

 thorax. Before proceeding to make a few additional remarks 

 and corrections to my former description of the pupa, it 

 w T ill be advisable, on account of the importance of the sub- 

 ject, to discuss the homologies of the limbs. 



From the presence of eyes and of two pairs of antennae 

 in the larva, during its earlier stages, the front of the 

 head consists, in accordance with all analogy, of three seg- 

 ments j the mouth, likewise, from being formed of three 

 gnathites (which can be detected by dissection in the pupal 

 state), consists, also in accordance with all analogy, of 

 three segments, making altogether six segments — on the 



