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 lamelle 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 lamell, 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 
Zs\ portion, the tissues contain great numbers of microscopic 
au 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 
ig 
ig. 
* On the anatomy of the A. coriacea, by T. P. Teale, Trans. Leeds Phil. and Lit. 
: ual ee 
Soc., vol. i, I have seen only the abstract given in Johnston’s British Zoophytes. 
