32 ZOOPHYTES. 



during the animal's contraction. In a papillose species, from the 

 Peruvian coast, examined by the author after preservation in alcohol, 

 each papilla contained a dark oval cavity, which communicated with 

 the interior by a distinct duct opening in a minute puncture between 

 the fleshy lamellae of the visceral cavity. 



As in other animals, a proper epidermis may be distinguished over 

 the exterior skin; and the colours, which are often brilliant and 

 various, are distributed in patches, according to Teale, below the 

 epidermis, and do not form a separate layer.* Different individuals 

 of the same species are often very unlike in their tints. 



The only external organs in these animals are the mouth and 

 tentacles. 



23. The mouth, as in the preceding order, is a simple opening 

 through the fleshy disk. It is usually oblong, and sometimes the inner 

 surface is raised into vertical folds or lobes. While the animal is 

 expanded, it remains open, and is usually much protruded, so as to 

 be quite prominent. 



24. The tentacles are slender organs, having generally a smooth 

 or simply granulous exterior, and terminating in a minute punc- 

 ture. They are tubular, and are inflated by water injected into 

 them by the animal. The interior cavity opens into the visceral 

 cavity between the visceral lamellse, and it is through this cavity and 

 its compartments that the distending water reaches the tentacles. On 

 contraction, the water passes out again through the puncture at the 

 extremity of some or all of these organs. The tubular interior, as 

 observed by Dr. Wyman, in the A. marginata, is constricted near 



the apex of the organ, and then undergoes a slight enlarge- 



* ' ment before it terminates in the apical puncture. In the upper 

 *^ portion, the tissues contain great numbers of microscopic 



spicules of the form represented in figure 13. They are 

 pellucid, like the body of the spermatozoa, but are only one-third as 

 large. 



The tentacles are seldom arranged in regular series, although 

 usually forming together a circle around the disk. On close exami- 

 nation, they are seen to differ in size and to be placed a little irregu- 

 larly ; and in some species they are scattered over the surface of the 

 disk nearly or quite to the mouth. They have some relation in 



* On the anatomy of the A. coriacea, by T. P. Teale, Trans. Leeds Phil, and Lit. 

 Soc., vol. i. I have seen only the abstract given in Johnston's British Zoophytes. 



