38 COMPARATIVE ANATOMY. 



mouth, together with the whole of the peduncle, is the result of 

 an extraordinary development of the pre-oral 'somites' and 

 the only appendage to be found in relation with these segments 

 is a pair of sucker-like antennae, to be seen by careful examina- 

 tion of the attached surface of the peduncle. 



55. A Barnacle (Lepas fascicularis) , dissected to shew its 

 digestive system. 



One half of the calcareous carapace has been removed, to- 

 gether with the investing membrane and the left testicular 

 mass. A black bristle has been inserted through the mouth and 

 oesophagus into the stomach, and a white one into the anus. 

 The mouth, encircled by its mandibles and maxillae, leads by a 

 short oesophagus into a large oval or sub-globular stomach. 

 The intestine is a simple tube of considerable size at its com- 

 mencement. It bends upon the stomach, and proceeds along 

 the dorsal aspect of the animal, gradually diminishing in size, 

 to the anus, which is situated at the base of the penis. 



Upon the stomach is a mass of dark-coloured glandular 

 caeca, probably hepatic in function, (a portion has been re- 

 moved with the wall of the stomach,) which communicate 

 by several large orifices with its cavity. The cuticular lining 

 of the oesophagus is continued for some distance into the 

 stomach, and terminates therein by a well-defined serrated 

 edge. 



56. The same, dissected, to shew its hermaphrodite genera- 

 tive system. 



In the upper of the two specimens on the tablet the cara- 

 pace and investing membrane have been removed, and the 

 organs displayed in situ, on the left side. 



The testis, of irregular shape, is composed of minute branch- 

 ing caeca, and not only overlies the pyloric end of the stomach, 

 but also gives off prolongations which enter the pedicels, and 

 the basal segments of the rami of the cirri. 



In the lower specimen a great part of the testis has been 

 removed, so as to shew the ' vas deferens,' or dilated portion of 

 the efferent duct of the testis, ascending parallel to the terminal 

 portion of the intestine. It gradually diminishes in size to the 

 base of the penis, where it joins the corresponding duct of the 

 opposite side to form the common canal, which, after traversing 



