INTEGUMENT. 69 



MOLLUSCA. Polyzoa. Integument, represented by a struc- 

 tureless membrane, containing calcareous or siliceous parti- 

 cles, is received by pullulation into skeleton, q. v. 



Brachiopoda. Integument contractile, cleft, forming halves 

 to a mantle* placed in relation to shell, q. v.; bud-like pro- 

 cesses, as in Polyzoa. 



Tunicata. Within the integument (test) of Ascidia nu- 

 merous cartilage-like cells are in relation with a membranous 

 matrix. The matrix presents great diversities of structure, 

 representing, in fact, almost every known tissue. Thus in 

 one genus we have a test resembling cartilage ; in another, 

 bone ; in a third, connective tissue. In Ascidia the integu- 

 ment separates into two layers, but in Boltenia the tendency 

 is less evident. An epithelium results from the imperfect 

 metamorphosis of the integumental layer. A structureless, 

 homogeneous epidermis, is naked and wrinkled in Salpa, 

 furnished with spines, or tesselated in some species of Bol- 

 tenia. The integument of Tunicata possesses the remarkable 

 property of elaborating cellulose. 



Lamcllibranchiata. The integument generally with two 

 openings, as in Tunicata one for the admission of water, 

 the other for its ejection. These often take the form of 

 tubes (siphons), more or less lengthened and projected at 

 will. The receiving siphon communicates with the cavity 

 included between the branchiae, the discharging one with an- 

 other cavity behind the leaves. In some species, however, 

 the discharging siphon is alone present. In Ostrea (oyster) 

 there are no siphons, the mantle being entirely open. (Gosse.) 

 Edges of mantle furnished with retractile papillae, rich in 

 glands and pigment cells. (For shell, see p. 26.) 



Gasteropoda and Pteropoda. Integument a dense con- 

 tractile derm of a cellular structure, often containing pig- 

 ment matter free or in cells. It is covered with a ciliated 

 epithelium, which partially or entirely covers the body. Its 



* ' Mantle' will be restricted to that fold or other portion of the integu- 

 ment designed to elaborate the shell. Where both shell and fold are absent, 

 'test' will be employed. 



