LYMPHATICS. 



[ 409 ] 



MACROBIOTUS. 



but is composed of a plexus of lymphatic 

 vessels closely connected with the efferent 

 vessels, supported by areolar tissue, without 

 elastic fibres, and containing a number of 

 fat-cells. 



The afferent lymphatic vessels penetrate 

 the capsule, pass through the septa between 

 the alveoli, and open into their lacuna, 

 which are not lined with epithelium. 

 From these the lymphatics of the medullary 

 plexus arise, to terminate in the efferent 

 vessel or vessels. 



It is supposed by some physiologists that 

 most of the chyle- and lymph-corpuscles are 

 formed in the lymphatic glands, and from a 

 formative blastema poured out by the capil- 

 laries of the alveoli. 



BIBL. Kolliker, Mikrosk. Anat. ii., and 

 the Bibl. therein; for the pathology, the 

 works of Forster and Wedl. 



LYMPHATICS. Absorbents or lymph- 

 vessels. 



The structure of the lymphatics is much 

 the same as that of the veins, but in some 

 respects it is obscure. 



In regard to that of their capillaries, little 

 positive is known. Lymphatics of interme- 

 diate and large size consist of three coats. 

 The internal is composed of somewhat elon- 

 gated epithelial cells, and an elastic reticular 

 layer of longitudinal fibres. The middle 

 coat consists of transverse muscular fibres, 

 with fine elastic fibres also transverse. The 

 outer areolar coat is composed of longitu- 

 dinal fibres, with a few reticular elastic 

 fibres, and a larger or smaller number of 

 oblique and longitudinal bundles of unstri- 

 ated muscular fibres ; the latter form a good 

 distinguishing character of lymphatics from 

 small veins. 



The thoracic duct differs somewhat in 

 structure from the lymphatics. Outside the 

 epithelium are some striated layers, next to 

 which is an elastic reticular layer, the fibres 

 being longitudinal ; but the entire inner coat 

 is thin. The middle coat consists of an 

 inner very thin longitudinal layer of areolar 

 tissue, with fine elastic fibres, and an outer 

 transverse muscular layer, containing also 

 fine elastic fibres. The outer coat contains 

 longitudinal areolar tissue, with elastic fibres 

 and scattered anastomosing longitudinal 

 bundles of muscular fibres. 



The valves of the lymphatics agree in 

 structure with those of the veins. 



LYNGBYA, Ag. A genus of Oscillato- 

 riaceae (Confervoid Algae), related to Calo- 

 thrix and Oscillatoria, distinguished from 



the former by its stratified habit, from the 

 latter by the long flexile filaments. It con- 

 tains both freshwater and marine species. 

 Hassall seems to have made strange errors 

 with the plants included under Lyngbya in 

 his work on Freshwater Algae, for Ulothrix 

 and Sphceroplea belong to a totally distinct 

 group. L. muralis (PI. 4. fig. 10) grows in 

 damp places and in w r ater. The specimen 

 from which our drawing was made exhibited 

 a remarkable motion, a snake-like advance 

 and retreat, coiling round other Confervae, 

 and waving also at the end like an OSCIL- 

 LATORIA. L. copulata, Hass. probably be- 

 longs to the genus. The rest of his species 

 belong apparently to ULOTHRIX. Harvey 

 describes five marine species, some of which 

 are of purple colour. 



These plants appear to break up into 

 lenticular gonidia, but their reproduction, 

 like that of Oscillatoria, is very obscure. 



BIBL. Hassall, Brit. Fr. Alg. p. 219. 



pi. 59. 60. 72; Harvey, Brit. Mar. Alg. p. 

 ~. pi. 26 E.; Kiitz. Spec. Alg. p. 279, 

 Tab. Phyc. i. pi. 86-90. 



225. pi. 26 E. ; Kiitz. Spec. Alg. p. 27! 



36-' 

 LYSIGONIUM. See MELOSIRA. 



M. 



MACROBIOTUS, Schultze. A genus of 

 Arachnida, of the order Colopoda, and family 

 Tardigrada. 



Char. Head not furnished with append- 

 ages ; mouth terminated by a sucker, without 

 palps ; skin soft, with irregular rugae. 



M. Hufelandii (PI. 41. fig. 8). Body cy- 

 lindrical, colourless ; head rounded in front, 

 with minute coloured eye-spots ; sucker, 

 pharyngeal tube and styles well developed ; 

 cesophageal bulb supported by a solid frame- 

 work of jointed pieces; legs equal; claws 

 two, bifid, the point of each again bifid; 

 movement tolerably quick ; size 1-85 to 

 1-35". 



The most common species; found upon 

 mosses growing on walls, stones, at the foot 

 of trees, &c. 



M. Oberhauseri. Dark brown ; colour dis- 

 tributed unsymmetrically in spots, and form- 

 ing five longitudinal bands ; no eye-spots ; 

 claws three, one simple, terminal, and form- 

 ing a short filament ; the two others hooked, 

 the anterior one double or bifid, the posterior 

 simple; movement very active; length 1-100 

 to 1-85". 



M.ursellus. Claws three, none filamentous. 



M. Dujardinii. Claws two, bifid. 



BIBL. Doyere, Ann. d. Sc. nat. 2nd ser. 

 xiv. xvii. and xviii. ; Dujardin, ibid. x. 



