158 



LECTURE XIII. 



Although the Cirripedes in their mature state possess no distinct 

 organs of sight or hearing, yet they are endowed with sufficiently 

 acute sensation to retract their cirri, and, if sessile, to close their 

 opercules, at the sound or vibration of an approaching footstep ; the 

 same actions indicate that they appreciate the atmospheric movements 

 produced by the approximation of the hand, even, according to Dr. 

 Coldstream, when it is not brought nearer the shells than twelve or 

 fourteen inches. 



The marine animalcules brought to the mouth i^fig. 86. «), by the 



currents of the cirrigerous 

 feet (h) and seized by the la- 

 teral jav>s, are conveyed by a 

 short oesophagus to a dilated 

 stomach (c), which receives 

 the ducts of two salivary 

 glands.. Groups of hepatic cseca 

 are developed from the walls 

 of the stomach. The intestine 

 (c?) is bent upon the stomach, 

 and tapers with a slightly 

 sinuous course to terminate 

 at {d) the base of the caudal 

 appendage (e). According to 

 M. St. Ange, the intestinal 

 canal of the Lepas contains 

 a membranous tube, which is 

 continued above into the se- 

 cerning cells in the walls of 

 the stomach; it may be the detached epethelium; it has been 

 deemed analogous to the typhlosole in the earth-worm's intestine. 



A dorsal vessel and circulating currents along a double canal in the 

 arms have been recognised ; but the circulating system has not been 

 thoroughly investigated. In the pedunculated Cirripedes slender 

 conical branchiae (/) are attached to the base of the maxillary foot, 

 and to that of some of the cirrigerous feet. The ordinal distinction 

 between the pedunculated and sessile Cirripedes is not less strongly 

 manifested by their outward forms than by the branchial organs, which, 

 in the Balanoids, consist of two or more broad, transversely plicated, 

 vascular membranes, attached to the inner surface of the mantle. 



The organs of generation in the Cirripedes have been differently 

 described by different authors. If the Cirripede be dioecious, and the 

 males be free and of a disproportionately minute size, as in the Epizoa 

 and in most Entomostraca, to which the Cirripedes are closely allied. 



Lepas. 



