ANGULAR APERTURE. [ 48 ] 



ANIMAL KINGDOM. 



object-glass, from the higher refractive 

 power of the immersion-liquid, which pro- 

 duces the effect of an increased angle of 

 aperture in the object-glass. This admis- 

 sion of an increased number of oblique rays, 

 would tend to invalidate the view, that the 

 more delicate structures are rendered visible 

 by the removal from the field of certain 

 olblique rays; but it would favour the 

 rendering of the markings visible by their 

 lenticular foci. According to the diffrac- 

 tion-theory, the admission of a larger num- 

 ber of diffraction-results would explain the 

 increased distinctness resulting from the 

 immersion-arrangements. 



Many rather controversial articles on the 

 relation of the dry- to the immersion-aper- 

 tures will be found in the M. M. Jn. from 

 1872 to 1877. 



It was noticed by Goring, that although 

 the lines on the scales of certain insects re- 

 quired an object-glass of comparatively 

 large aperture to show them, yet those ex- 

 isting upon glass micrometers did not so. 

 But this statement is only partially correct ; 

 for although the coarser lines upon micro- 

 meters are well seen under an object-glass 

 of small aperture with good defining power 

 and direct light, yet the finest lines upon 

 Nobert's test-slide require penetrating power 

 in the object-glass, and oblique light. Thus, 

 R. Beck found that a ^th-in. object-glass of 

 120 would show all the 20 sets of Nobert's 

 lines; when cut down to 110, it would not 

 resolve the 20th band ; at 100 the 17th 

 was the limit ; at 80 the 14th ; and at 60 

 the 10th. 



Our space will not permit of entering into 

 further details on this important matter ; 

 but we shall refer to it again, in its relation 

 to the markings on the DIATOMACEJE. 



Apertures of Object-glasses. The follow- 



ing apertures of (dry) object-glasses may be 



taken to represent those usually met with 



in good glasses : 2", 14 ; 1", 25 ; ", 32 



", 400-80; i",75-140; T, 140; 



; ft", 

 . The 



145-170; 5 y, 160; and ^y, 150. e 

 apertures of the foreign object-glasses are 

 usually over-estimated by the makers in 

 their price-lists. 



The transverse lines seen upon the scales 

 of insects are noticed under SCALES of IN- 

 SECTS. The structure of the valves of the 

 DIATOMACEJE is discussed under that head ; 

 see also INTRODUCTION, p. xxxix, I. 



BIBL. Lister, Phil. Tr. cxxi. ; Goring, 

 Micrographia ; Pritchard, Micr. Cabinet ; 

 R. Beck, Treatise fyc. 19; Wenham, M. 



M. J. 1872, viii. 231 & 1876, xvi. 285 ; 

 id. Jn. Mic. Soc. 1878, i. 321; Abbe 

 (abridged by Fripp), M. M. Jn. 1875, xiv. 

 191, 245 ; id. (Theor. d. Mik.) Arch. f. nn'k. 

 An. 1873, ix. 420; (estimation of aperture) 

 Jn. Mic. Soc. 1881, i. 388; Apertometer 

 (figs.), Jn. Mic. Soc. 1880, iii. 20; Helm- 

 holtz (Theor. Grenze f. d. Leist.), Poggen- 

 dorff's Ann., Jubelband, 1874, g. 566 ; Ste- 

 phenson, M. M. Jn. xiv. 3 & xvii.82; Nageli 

 andSchwendener, Mikr. 1877, p. 82 ; Stokes, 

 Jn. Mic. Soc. 1878, i. 139; F. Crisp, 

 Jn. Mic. Soc. 1881, i. p. 303 (full description 

 and illustrations of Abbe's views) ; Wenham, 

 Amer. Jn. Micros. 1881. 



ANIMALCULE. A little animal; a 

 term usually applied to the Infusoria, Ro- 

 tatoria, &c. It was formerly applied also 

 to many of the lower Algae. The Latin 

 term animalculum (plural animalculd) is 

 frequently met with. 



ANIMAL KINGDOM. In accordance 

 with our plan, as laid down in the Preface, 

 we give here a tabular view of the animal 

 kingdom, so that the position of the various 

 classes and orders alluded to in various parts 

 of this work may be readily found. Those 

 classes, orders, families, and genera to which 

 particular interest is attached in relation to 

 structure or other qualities, which the micro- 

 scope is required to investigate, are specially 

 treated of under their respective heads. 



Kingdom ANIMA'LIA. 

 Subkingdom I. VERTEBRA'TA. 

 Class I. MAMMA'LIA. 



Order 1. BI'MANA. 



Homo, man. 

 Order 2. QUADRU'MANA. 



Simia, ape; Cercopithecus, common 

 monkey; Semnopithecus, Indian mon- 

 key. 

 Order 3. CHEIROP'TERA, 



Vespertttio, bat. 

 Order 4. INSECTI'VORA. 



JErinaceus, hedgehog ; Talpa, mole. 

 Order 5. CARNI'VORA. 



Cams, dog and wolf; Ursus, bear; 



Felis, lion ; Nasua, coatimondi. 

 PINNIPEDIA. Phoca, seal. 

 Order 6. CETA'CEA. 



Bal&na, whale ; Plioccena, porpoise. 

 SIRENIA. Halicore, dugong ; Manatus, 

 manatee. 



Order 7. PACHYDER'MATAf. 



Equus, horse ; Sus, hog ; Hippopota- 

 mus ; Choir opatamu8. 



