OF THE ROTATOEIA. 395 



used by Ehrenberg, being alike applied to the soft, pliant skin, to the hard 

 shell-liie cuticle, and to the loose and large external cases in which some 

 Botatoria live, as do the Coralline Polypes, in a cell or chamber. If limited, 

 however, in its signification, as above suggested, the term may still be use- 

 fully retained, and is preferable to the word ' shell,' which peculiarly belongs 

 to the habitation of the Mollusca. By some authors the term carapace is 

 emiDloyed ; but to this there occurs a similar objection. 



The lorica received from Ehrenberg various names, according to its form. 

 Where a firm cuticle entirely enveloped the trunk, lea\dng the head and tail 

 free, it constituted a testula, as in Pterodina ; where it covered only the upper 

 surface and sides, it formed a scutellum or shield, as in Monura (XXXTV. 

 457-459). The term ' carapace,' employed by some authors, is equivalent 

 to scutellum. The anterior and posterior openings of a testule vary much in 

 different species ; and an equal diversity occui's in the space left uncovered 

 by a scutellum. This space is small and very narrow in Euclilanis Lynceus, 

 in E.pyi-iformis, and in E. dejiexa. In the last, moreover, the free edges are 

 bent outwards at right angles. In several genera, again, the lorica appears 

 composed of an upper and an under plate, or is, in other words, bivalved. 

 This is seen in Dinocharis (XXXIV. 454, 455), Salpina, and Colurus, and 

 resembles the envelope in some of the lower Crustacea, as Cypris. In a few 

 Rotifera, e. g. Euchlanis (XXXYIII. 5), the lorica aj)pears much too large, 

 the contained viscera only partially filling it. An increased firmness of the 

 lorica enables it to resist decomposition longer than its soft contents ; hence 

 the occurrence of empty ones. Where the integument is of sufficient firmness 

 to present an anterior and posterior margin, it is subject to many variations 

 in form. Thus it may be truncate in front, as in Hydatina, Dlglena 

 (XXXIII. 403-405), and Polyartlira (XXXVIII. 30) ; or behind, as in 

 Notommata Felis. It is crescentic in Metopidia ; deeply and widely notched 

 in Lepadella patella ; has several spines, in front only, in Anura^a ; and both 

 anteriorly and posteriorly in Noteus, Salpina (XXXIY. 447-453), and Bra- 

 chionus (XXXIY. 499-501). Sometimes the spines are so short and vdde, 

 that the border appears simply dentated or undulated ; in other cases, spines 

 may be long and strong, and themselves dentated, as in Noteus quadricornis 

 (XXXYIII. 25). Not only do the anterior and posterior margins differ, but 

 even those of the upper and under surface of the lorica, for example, in 

 Salpina spinigera and in S. mucronata. Animals with spines projecting from 

 the anterior margin, Ehrenberg speaks of as '^ homed.' 



The surface of the integument is variously modified. Ths slightest change 

 from the normal smooth condition consists in a shagreened, dotted, or stippled 

 surface, or in the presence of fine lines, — e. g. in Amurea inermis, Dinocharis 

 and Diglena lacustris. In Notommata centrura, fine silky prominences clothe 

 the surface. In Noteus quadricornis and Brachionus militaris, the points are 

 elevated, and give the surface a rough (scabrous) aspect. Lines crossing each 

 other, producing a tessellated or reticulated condition, are seen in Anm^cea 

 curvicornis and in Brachionus BaTceri ; whilst in Anuixea testudo, Brachionus 

 militaris (XXXIX. 21, 22), and Noteus quadricornis (XXXYIII. 25) the 

 lines assume the character of ridges, and divide the surface into squares or 

 facettes. Radiating or curved strise are seen in Anuroea striata and A. 

 foliacea, which in Euchlanis Lynceus are replaced by flutings. 



The elevated points may assume a further development, and project fi'om 

 the surface in the form of ciu'ved spines or hooks (acidei), as in Philodina 

 aculeata ; or they may be so extended in length as to form long spines or 

 rigid styles or setae having particular functions, as in Triarthra (XXXYIII. 

 30, 31, 32), and Polyarthra, where they are important organs of locomotion. 



