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



criterion. On the other hand, from the morphological standpoint, they are to he classed as neutral 

 Protista, for in this respect their unicellular character is the prominent feature, and distinguishes 

 them from all true multicellular animals (Metazoa). Compare my Gastrsea Theorie (1873, Jena. 

 Zeitschr. fiir Naturwiss., Bd. viii. pp. 29, 53). 



204. Nutrition. — The nutritive materials wticli the Eadiohiria require for their 

 sustenance, especially albuminates (plasma) and carbohydrates (starch, &c.), they obtain 

 partly from foreign organisms which they capture and digest, and partly directly from 

 the Xanthellse or Philozoa, the unicellular Algae, with which they live in symbiosis 

 (§ 205). Zooxanthella intracapsularis, found in the Acantharia (§ 76), is probably of 

 the same significance in this respect as Zooxanthella extracapsularis of the Spumel- 

 LAEIA and Nassellaria (S 90) ; and perhaps the same is true also of Phceodella extra- 

 capsularis (or Zoochlorella phcBodaris ?) of the Ph.5:odaria (§ 89). The considerable 

 quantity of starch or amyloid bodies, elaborated by these inquiline symbioutes, as well 

 as their protoplasm and nucleus, are available, on their death, for the nutrition of the 

 Radiolaria which harbour them. Nutrition by means of other particles obtained by the 

 pseudopodia from the surrounding medium is by no means excluded ; indeed it may be 

 regarded as certain that numerous Radiolaria (especially such as contain no symbiotic 

 Algoid cells) are nourished for the most part or exclusively by this means. Diatoms, 

 Infusoria, Thalamophora (Foraminifera) as well as decaying particles of animal and 

 vegetable tissues can be seized directly by the pseudopodia and conveyed either to the 

 sarcodictyum (on the surface of the calymma) or to the sarcomatrix (on the surface of 

 the central capsule) in order to undergo digestion there. The indigestible constituents 

 (siliceous shells of Diatoms and Tintinnoidea, calcareous shells of small Monothalamia 

 and Polythalamia, &c.) are here collected often in large numbers and removed l^y the 

 streaming of the protoplasm. 



The inception and digestion of nutriment, as it usually appears to take place by the pseudo- 

 podia, has already heen so fully treated in my Monograph (L. N. 16, pp. 135-140), and since then 

 in my paper on the sarcode body of the Ehizopoda (L. N. 19, p. 342), that I have nothing of 

 importance to add. Quite recently Karl Brandt has expressed a doubt as to whether the taking up 

 of formed particles by the pseudopodia and their aggregation in the calymma be really connected 

 with the process of nutrition. He is disposed rather to believe that these foreign bodies are usually 

 only accidentally and mechanically brought into the calymma, and that the nourishment of the 

 Eadiolaria is derived exclusively or pre-eminently from the symbiotic Xanthellje (L. N. 52, 

 pp. 88-93). I must, however, maintain my former opinion, which I have only modified insomuch 

 that I now regard the sarcodictyiim (on the outer surface of the calymma, § 94) rather than the 

 sarcomatrix (on the outer surface of the central capsule, § 92) as the principal seat of true 

 digestion and assimilation. From the sarcodictyum the dissolved and assimilated nutritive matters 

 may pass by the iutracalymmar pseudopodia (or sarcoplegma, § 93) into the sarcomatrix, and hence 

 may reach the endoplasm through the openings in the central capsule. To what an extent the 

 Eadiolaria are capable of taking up even large formed bodies into the calymma, is shown by the 



