. Biology . ion ofblood to the body cavity throughmuscular heart beats, aided by thevacuum produced when the heartis emptied. Movements of theappendages also tend to keep upa constant circulation in thesinuses. The Excretory System.—Ex-cretion in the lobster must becomparatively sluggish, for theorgans for the purpose are smalland poorly placed for active func-tion. This may be due to the factthat the lobster and similar formsare naturally sluggish animals,lying in wait for prey, feeding oncarrion, etc., rather than movingabout actively in search of nephridia are small flattenedcoiled
. Biology . ion ofblood to the body cavity throughmuscular heart beats, aided by thevacuum produced when the heartis emptied. Movements of theappendages also tend to keep upa constant circulation in thesinuses. The Excretory System.—Ex-cretion in the lobster must becomparatively sluggish, for theorgans for the purpose are smalland poorly placed for active func-tion. This may be due to the factthat the lobster and similar formsare naturally sluggish animals,lying in wait for prey, feeding oncarrion, etc., rather than movingabout actively in search of nephridia are small flattenedcoiled organs at the bases of theantennules, and consist of a ratherlarge bladder and a smallglandular part (Fig. 71). Fromtheir characteristic color they arealso known as the green external openings of the nephridial ducts are on theinner faces of the basal segments (Fig. 68, 3). Some excretionof waste matters may also take place through the skin. The Muscular System.—The muscles of the lobster are. Fig. 72.—The abdominalmusculature of the lobster toshow the complicated arrange-ment of extensors and flexors.(From Gerstaecker, after jMilne-Edwards.) 178 HOMOLOGY
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