ELACHISTEA. 



[ 221 



1 



ELAPHOMYCES. 



great symmetry, and frequently closely re- 

 sembling the cellular structure of plants in 

 apj)earance. Sometimes very delicate angular 

 spaces are mapped out upon them, the inter- 

 spaces being most minutely dotted, as in the 

 eggs of the common blow-fly, Musca vomi- 

 toria (PI. 27. fig. 35). 



It is a general fact, exemplified in both 

 the animal and vegetable kingdom, that 

 unicellular, or the corresponding stages or 

 phases of the higher organisms, exhibit some 

 kind of markings upon their external mem- 

 brane or wall ; as is seen in the cells of the 

 Desmidiaceae, the Diatomacese, the eggs of 

 animals, the seeds of plants (PL 31. figs. 14 

 to 19). 



At certain seasons of the year, the eggs of 

 aquatic animals are provided with a very 

 thick horny coat, as in the Entomostraca, 

 Hydra, &c. These have been called winter- 

 ova, from the notion that here was a defence 

 against a low temperature ; they correspond 

 to the resting-spores or resting-stages of the 

 Infusoria and Algae, some of which were 

 formerly included in the animal kingdom. 

 The formation of this coat can scarcely have 

 any relation to temperature, either from its 

 structure, or from its requirement in an or- 

 ganism which has no heat to retain. Its 

 presence would be perfectly intelligible, 

 however, as a means of protection from eva- 

 poration, when the pools become dry; and 

 for this purpose its structure is well adapted. 

 It might also aff'ord a protection against the 

 attacks of predatory animals, many of which 

 could easilv devour an ovarian ovvim, while 

 they could not break through the horny 

 cases of the winter ova ; and these \^dnter 

 ova are only formed when the ova are not 

 to be hatched soon after extrusion fi'om the 

 parent. The ova of those animals, which 

 are never hatched immediately after leaving 

 the parent, have always a coat corresponding 

 to that of the winter ova. 



The structure and development of eggs 

 are considered under Ova; see also Shell, 

 BiBL. See Ova. 



ELACHISTEA, Fries.— A genus of My- 

 rionemacese (Fucoid Algae). Minute epi- 

 phytic sea-weeds, consisting of a dense tuft 

 of simple, articulated, olivaceous filaments, 

 fi-om a common tubercular base composed 

 of a closely combined mass of dichotomously 

 branched filaments, growing upon larger 

 Fucoids, such as Fucus, Himatithalia, Cysto- 

 seira, &c. The fructification is borne in two 

 forms : oosporanges [spores, Harvey), and 

 trichosporanges {paranemata, Harvey). The 



oosporanges are formed of metamorphosed 

 terminal cells at the ends of the dichotomous 

 filaments ; they are long ovoid sacs, the con- 

 tents of which are ultimately converted into 

 a vast number of zoospores. The tricho- 

 sporanges arise in exactly the same place 

 and way, but take the form of long, slender, 

 articulated filaments, in the joints of which 

 similar but smaller zoospores are developed. 

 Both forms of fructification nestle on the 

 sm-face of the tubercle of the frond, at the 

 base of the long simple filaments. The zoo- 

 spores of both kinds of fruit germinate, and 

 these occur together in some cases {E. at- 

 tenuata), in others at diiFcrent seasons of the 

 year. Harvey describes seven British spe- 

 cies ; the tufts of some are half an inch long, 

 of others less than a line. 



BiBL. Harvey, Brit. Mar. Alg. p. 49. pi. 

 10 F; Phyc. Brit. pi. 240. 260, 261, &c. ; 

 Dillw. Conferv(S, pi. ^Q, &c. ; Thuret, Jnn. 

 des Sc. not. 3 ser. xiv. p. 236. pi. 25. figs. 

 1-4. 



EL^EAGNACEtE.— A family of Dicoty- 

 ledons, the leaves of which are usually co- 

 vered with a kind of scurf formed of very 

 elegant microscopic scales. See Hairs and 



HiPPOPHAE. 



ELAPHOMYCES, Nees.— A genus of 

 Tuberacei (Ascomycetous Fungi), consisting 

 of subterraneous truftle-like plants, with a 



Fig. 188. 



Fig. 187. Elaphoniyces hirtus. Section, nat. size. 



Fig. 188. E. variegatus. Filaments of capillitium, with 

 asci containing spores ; and also loose spores which have 

 escaped. Magnified 300 diameters. 



