SLIDES. 



[ 581 ] 



SNOW. 



of which, as those of the pulp of the finger, 

 form very beautiful objects. The epidermis 

 is easily separated by maceration. 



The integument of animals is noticed 

 under the respective heads of the'classes. 



It must be remarked that the terms epi- 



Fig. 650. 



Section of the skin of the heel parallel to the surface, 

 through one entire ridge of the skin and part of two 

 others ; showing the arrangement of the papillae in rows 

 corresponding to the ridges of the cutis. a, cuticle between 

 the ridges ; b, rete mucosuni ; c, papillae ; d, portion of 

 the rete mucosum between papillae arising from a 

 common base ; e, sudoriparous ducts. 



Magnified 60 diameters. 



dermis and cuticle are generally used syno- 

 nymously. 



BIBL. Kolliker, Mikrosk. Anat. i. and 

 Gewebelehre ; Krause, Wagner's Handwor- 

 terbuch d. Physiol. ii. 127; Weber, ibid, iii.; 

 Todd and Bowman, Phys. Anat. &c. 



SLIDES. INTRODUCTION, p. xxi. 



SMARIS, or SMARIDIA, Latr. A genus 

 of Arachnida, of the order Acarina, and fa- 

 mily Trombidina. 



Char. Palpi slender, inserted upon a re- 

 tractile rostrum ; mandibles sword-shaped ; 

 body entire, narrowed in front ; coxae stout, 

 distant, the anterior articulated to a fixed 

 eminence upon the body; legs palpatorial 

 (used also as palpi), the anterior longest. 



S. papillosa (PL 2. fig. 36; a, mandible). 

 Body vermilion-coloured, broader in front, 

 depressed, covered with short cylindrical 

 papillae rounded at the end. 



Found upon the trunks of trees, and in 

 moss. 



Fusiform scales replace the papilla3 upon 

 the legs, palpi, and rostrum. 



Several other species, found in moss, upon 

 fallen leaves, and on the debris left after in- 

 undations. 



BIBL. Duges, Ann. des So. nat. 2 ser. i. 

 16 & 34; Gervais, Walckenaer's Apt. iii. 

 173. 



SMUT. See UREDO. 



SNAILS, WATER-. Most microscopic 

 observers, ever anxious to determine the 

 unknown cause of the curious circulation or 

 rotation (ROTATION) taking place in certain 

 water-plants, as Vallisneria, Anacharis, &c., 

 keep these growing in large glass vessels, as 

 confectioners' jars, or other reservoirs (Vi- 

 varia). These plants, and the sides of the 

 vessels, are, however, very apt to become 

 overgrown and obscured by Confervoid Algae, 

 as (Edogonium, Palmellaceae, &c., which may 

 be prevented by keeping water-snails in the 

 water, as species of Lymneeus, Physa, Bithy- 

 nia, Planorbis, &c. The latter are best for 

 this purpose (the shell is flat-spiral). If Des- 

 midiaceae, Diatomaceae, Infusoria, &c. are to 

 be preserved, the snails must be carefully 

 excluded, because many of these are con- 

 sumed by them, and will not live, as the 

 bottom of the vessels soon becomes covered, 

 w r hen snails are kept, with a load of excre- 

 ment. The characters of the snails are too 

 long to be given here. The gelatinous masses 

 of ova are found adhering to water plants, 



See the Bibl. of MOLLUSCA. 



SNOW. The various forms presented by 

 ice or crystallized water in the form of snow 

 constitute beautiful although fugitive micro- 

 scopic objects. 



The crystals belong to the rhombohedric 

 or hexagonal system. Several hundreds of 

 forms have been observed, and many of them 

 figured. Among them may be mentioned 

 hexagonal or dodecahedral plates, hexagonal 

 prisms, single, arranged in a stellate form, 

 or terminated by rectangularly placed plates 

 or secondary groups of needles, hexagonal 

 pyramids, &c. The angles of these forms 

 frequently constitute secondary centres, 

 around which other similar or dissimilar 

 forms are aggregated. By some authors 

 these forms are regarded as skeleton crystals. 



See also RED SNOW. 



BIBL. Scoresby, Account of the Arctic 

 Regions; Kamtz, Meteorologies Glaisher, 

 Micr. Journ. 1855. iii.; Naumann, Elem. d. 

 Mineralogie. 



