Ix THE VOYAGE OF H.M.S. CHALLENGER. 



through the openings of the central capsule with the endoplasm, whilst externally the 

 pseudopodia or mucous threads arise from it, which by their union form the sarcoplegma. 

 The sarcomatrix is only interrupted in the SPUMELLARIA and ACANTHARIA by those 

 parts of the skeleton which perforate the membrane of the central capsule. In all 

 NASSELLARIA and PH^EODARIA, as in the Collodaria, it appears as a perfectly con- 

 tinuous sarcode-envelope of the central capsule. Its thickness is variable ; in general 

 it is most strongly developed in the SPUMELLARIA and PELEODARIA, less so in the 

 NASSELLARIA, and is thinnest in the ACANTHARIA. The thickness seems, however, to 

 vary even in one and the same individual, the difference depending partly upon 

 the different stages of development and partly upon nutritional conditions. After 

 abundant inception of nutriment the thin protoplasmic layer of the matrix is thickened 

 and turbid, rich in granules and irregular masses, which are probably due to enclosed 

 but only half -digested food; xanthellse also, as well as foreign bodies taken up with the 

 nutriment, such as frustules of Diatoms and shells of smaller Eadiolaria, and of pelagic 

 infusoria, larvae, &c., are often, especially in large individuals, aggregated in consider- 

 able quantities in the matrix. After long fasting, on the contrary, this is poor in these 

 enclosed bodies and in granules ; it then forms a thin colourless more or less hyaline 

 mucous coating to the central capsule. From a physiological standpoint the sarco- 

 matrix is to be regarded as the central organ of the extracapsulum, and as of pre- 

 eminent significance. Probably it is not only the most important organ for the 

 nutrition of the Radiolaria (especially for digestion and assimilation in particular), but 

 perhaps is also the central organ of perception. On the other hand the sarcomatrix 

 belongs to those components of the Radiolarian organism which take no part in the 

 formation of the skeleton. 



A. The sarcomatrix was first described in my Monograph in 1862 (p. 110) as the "Mutterboden 

 der Pseudopodien," possessing a pre-eminent physiological importance. Compare also my paper on 

 the sarcode elements of the Ehizopoda (Zeitschr. f. wiss. Zool., Bd. xv. p. 342, 1865). 



93. The Sarcoplegma. By the name sarcoplegma, as distinguished from the 

 remaining extracapsular sarcode, is understood the intracalymmar web of exoplasm 

 or " ectosarcode network," which ramifies within the gelatinous mass of the calymma. 

 Internally it is in direct connection with the continuous sheath (sarcomatrix), which 

 encloses the central capsule, whilst externally it is in contact with the superficial 

 sarcode network (sarcodictyum) which surrounds the calymma. The configuration of 

 this exoplasmic web, which penetrates the jelly-veil in all directions, is exceedingly 

 variable ; in most Radiolaria it is extremely irregular in form, like the protoplasmic 

 network in the ground-substance of many kinds of connective tissue. In some groups, 

 however, it assumes a rather regular shape which it appears to retain (e.g., in many 

 ACANTHARIA). It must be assumed also that in those instances where the consistency 



