878 THE ANIMAL KINGDOM. 



sheaths of the spines. The protoplasm forms a layer or sarcomatrix 

 immediately surrounding the central capsule ; it is massed over the single 

 aperture of the Nassellaria and the astropyle of Phaeodaria \ From this 

 layer a more or less irregular network of protoplasmic threads, the sarco- 

 plegma, radiates to the surface of the jelly, where it forms a superficial 

 network, the sarcodictyum, from which originate the pseudopodia. These 

 structures vary in length and number ; they are radiant, but may anas- 

 tomose, especially in Nassellaria and Phaeodaria, two groups in which the 

 sarcoplegma and pseudopodia are chiefly derived from the protoplasm 

 issuing from the single aperture of the one or principal aperture of the 

 other. In Acantharia the pseudopodia are disposed in an orderly way, 

 and certain of them, the axopodia, either placed one between each pair of 

 spines, or surrounding in a circle the bases of the spines, are supported by 

 stiff axial filaments penetrating the central capsule. Some Discoidea 

 possess also a single thick striated sarcode-flagellum, of eminently con- 

 tractile nature, but otherwise motionless, formed by the fusion of pseudo- 

 podia and traceable as far as the nucleus. Peculiar protoplasmic pro- 

 cesses or myophrics, 5-30 or more, extend from the edges of the calymnal 

 sheaths to the apices of the spines in Acantharia. They are contractile 

 and expand the calymna. At death they are set free from the spines and 

 remain projecting from the sheaths as the so-called ' ciliary coronas ' or 

 ' gelatinous cilia.' The protoplasm of the sarcomatrix, &c., is more or less 

 granular ; some of the granules consist of fat ; oil-globules occur in the 

 large Collodaria, albumen globules in Thalassolampe primordialis and Collo- 

 zoum. Vacuoles formed in the course of the sarcoplegmal threads and of 

 small size are found in most Radiolaria. Large vacuoles are confined to 

 the Collodaria and a few Sphaeroidea among Spumellana, to Nassella, and 

 some Plectoidea among Nassellaria, and to the Phaeocystina. They are 

 frequently so numerous as to give the calymna a frothy appearance. When 

 the animal is irritated they disappear progressively from the periphery to- 

 wards the centre, but are formed anew when it is left at rest. In some 

 colonial forms, e. g. Collosphaera, the central part of the colony is occupied 

 by a soft sphere of jelly 2 . Black or blue pigment occurs in some large 



1 The sarcomatrix is said by Biitschli (Protozoa, p. 431) to be wanting at the apical or aboral 

 pole of the Nassellarian Cystidium and Plagiacantha. Haeckel states (op. cit. supra, p. Ixvii.) that 

 it is often so thin at this spot in Nassellaria that it can be demonstrated only by reagents. Brandt 

 points out that the sarcomatrix, as well as spindle-shaped masses in the sarcoplegma of Collozoum 

 inerme, C.fulvum, Sphaerozoum neapolitanum, Sph. acuferum stains strongly with osmic acid, and 

 violet with iodine, while the rest of the protoplasm of the body does not do so. To the portions 

 which stain he gives the name of ' Assimilation-plasma.' In Siphonosphaera tenera it is aggregated 

 in masses, each of which has 2-5 central capsules round it. See his monograph cited, pp. 14-15, 18, 

 92-4. The same authority describes (p. 21) globular or plate-like masses of protoplasm in the 

 sarcoplegma of young Collozoa, especially C. pelagicum, and in Acrosphaera spinosa, which contain 

 brownish granules, and are perhaps connected with vacuole- formation. 



2 The distinction between true vacuoles and alveoles, mentioned note 2, p. 876, is applied by 



