128 BALANID^l. 



the anterior extremity, however, soon becomes cemented 

 down, and afterwards, in ordinary cases, ceases to grow. 

 In Crvptophialus, however, and in certain genera of the 

 Lepadidae, as Alcippe, Lithotrya, and Anelasma, the anterior 

 or basal extremity does continue to grow, and is not cemented 

 down, and therefore comes to be prolonged beyond the ori- 

 ginal point of attachment ; in order to allow of this, the 

 surface to which the Cirripede is attached has to yield, appa- 

 rently simply to the pressure exerted in the case of Anelasma, 

 but in the three other genera, to the rasping action of the 

 roughened surface of the extremity of the peduncle. 



When after a period the pupal membranes of the sack, 

 thorax, and natatory legs are moulted, the cirri of the 

 young Cirripede are curled up, and its thorax is raised 

 towards the orifice, and we have the animal in its ordinary 

 position, and perfect with the exception of a few parts to 

 be further developed or modified. For, instead of calcareous 

 valves, we have at this period only the so-called primordial 

 valves, composed of chitine ; and in the case of Lepas 

 australis, some minute spines and some coloured marks on 

 the peduncle, which soon disappear. The muscles, which 

 enter the three terminal segments of the antennae in the 

 pupa, have to be absorbed and converted into ligamentous 

 threads. In Lepas, the labrum has to become bullate ; and 

 the caeca have to increase in number round the upper end 

 of the stomach, and their dark colour and that of the whole 

 alimentary canal has to disappear or be much weakened. 

 The filamentary appendages at the bases of the cirri, which 

 generally contain some of the testes, have to be developed. 

 The probosciformed penis, which at first equals only the 

 pedicels of the posterior cirri in length, and is apparently 

 imperforate, has to increase greatly in length. The testes 

 and vesiculae serninales have to be formed. And lastly, and 

 this is a more important point, the two gut-formed cement- 

 glands (or incipient ovaria, t, fig. 2, PI. 30) which, at the 

 period of the moulting of the carapace and eye-apodemes, 

 and when the whole animal was upturned, came to occupy, 

 together with the cement-ducts (f), their normal position, 

 i. e. nearly parallel to the sternal surface, now undergo fur- 

 ther changes. Their upper and posterior ends lying near 



