ACAULON. 



ACII1TA. 



f. 5. Sarcoptes muse., Koch, Crust. $c. 

 fasc. 5. pi. 13 ; On the mouse, Murray, p. 315. 



Hypopus. See HYPOPUS. 



A destructive disease in the sugar-cane is 

 caused in various parts of the world by a 

 minute red Acarus, which swarms round 

 the stem. 



BIBL. Duges, Ann. d. Sc. Nat. 2 se"r. ii. 

 p. 40 ; Koch, Deutschl. Crust. ; Walckenaer, 

 Aptcres, 3 (Gervais) ; Fumouze and Robin, 

 Jmirn. d. VAnat. 1867, 505, 561 ; Boisduval, 

 ISEntomol. horticole, p. 76; Mic. Soc. 

 Jn. 1880,^/1/0. dev. p. 249; Murray, J%.jBi& 

 1880 ; Megnin, Parasites, 1880. 



AOAU'LON, C. Miiller. A genus of 

 Phascaceae (Acrocarpous Mosses), taken as 

 a section of Phascum by Wilson. A. muti- 

 cum is common on moist banks. 



BIBL. Miiller, Synops. Muse. i. p. 21 ; 

 Wilson, Bryol. Brit. p. 29. 



ACEPH'ALpOYSTS. A term used to 

 denote certain simple sacs filled with a trans- 

 parent liquid, found in the bodies of ani- 

 mals, and usually known as Hydatids by 

 pathologists. They were formerly regarded 

 as distinct parasitic animals ; but recent 

 observations show that they often consist of 

 the cysts or larval forms of cestoid Entozoa. 

 The cysts in many cases contain at first 

 only an amorphous substance or a liquid. 

 At a later period their real nature is deter- 

 mined by the presence of the included 

 Echinococcus head and hooks. The sacs 

 or vesicles are oval or spherical, and vary 

 in size from a pin's to a child's head. The 

 walls of the sacs vary in thickness and 

 transparence. They present no appearance 

 of either head or body. In the larger cysts 

 the walls are distinctly laminated. They 

 exhibit no fibrous structure, but appear 

 composed of a homogeneous substance 

 closely resembling albumen in properties. 

 Two species have been distinguished : 



A. endogena (socialis vel proliferd), the 

 pill-box Hydatid of Hunter. This is met 

 with in the liver, kidney, ovary, testis, and 

 cavity of the abdomen. When developed 

 in the substance of an organ, it is always 

 enveloped by areolar tissue. The secondary 

 cysts are detached from the inner surface of 

 the parent. 



A. exogena : in this the progeny is de- 

 veloped from the outer surface ; found in 

 the ox and other dometic animals. 



In the examination of cysts supposed to 

 be hydatids, careful search should be made 

 for the hooks of Echinococcus or Cysticercus 

 which can frequently be found when no 



further remains of the body are distingui .-li- 

 able. The hooks are figured in 1*1. 21. 

 fig. 16. See ENTOZOA and ECHINOCOC- 

 CUS. 



ACERVCJLI'NA, Schultze. Under this 

 name Schultze, in 1854, grouped as a genus 

 some of the adherent varieties of Planorlu- 

 lina variabilis, D'Orb., that have an irregular 

 growth, with heaped chambers. They are 

 found in warm seas, attached to algae and 

 other bodies. The word "acervuline" is 

 applied to any such ' wildly aggregated 

 growth in Foraminifera. 



BIBL. Schultze, Organism. Polythal. 67 ; 

 Carpenter, Forum. 209. 



ACETIC ACID. This is the well- 

 known acid of vinegar. 



It occurs in the juice of the flesh of ani- 

 mals ; sometimes in the stomach in indiges- 

 tion ; also in the human blood after the use 

 of alcoholic liquors, and in that of animals 

 whose food has been soaked in spirit. It is 

 also a common product of the decomposition 

 of vegetable substances, both by fermenta- 

 tion, and in distillation, as well as a com- 

 ponent of the natural plants, mostly com- 

 bined with lime or potash ; it is also a rare 

 constituent of some mineral waters. 



The only salt of this acid requiring men- 

 tion is the acetate of copper (neutral), which 

 is made' by dissolving common verdigris in 

 excess of dilute acetic acid, filtering and 

 crystallizing upon the slides. The crystals, 

 when mounted in Canada balsam, exhibit 

 well the phenomena of dichroisin. PL '39. 

 fig. 2. 



Acetic acid is one of the most common 

 and valuable micro-chemical reagents. It 

 is particularly useful on account of its action 

 upon animal cells in general, rendering the 

 coil-walls transparent and the nuclei more 

 distinct. The ordinary strong acid (sp. gr. 

 1044) should be used. 



ACETINOP'SIS, Kent A genus of Iii- 

 fusoria, family Ophryodendridae. 



BIBL. Kent, Man. Infus. 1880. 



ACHARAD'RIA, Wright. A genus of 

 11 yilroid Zoophytes. 



A. larynx resembles in habit Tulmlaria 

 larynx ; polypes orange. Marine ; on stones. 



BIBL. Str. Wright, Qu. Mic. Jn. 1865, 

 iii. p. 50 ; Hincks, 'Brit. Zoophyt. p. 133. 



ACHE'TA. A genus of Orthopterous in- 

 sects, one species of which, A. domestica, the 

 house-cricket, is familiar to every one. The 

 general structure of this insect agrees so 

 closely with that of Blatta orientalis, the 

 common cockroach or black beetle, which is 



