REPORT ON THE RADIOLARIA. Cxliii 



well-being of the organism, both as sensory organs and as prehensile organs. By far 

 the most important and most varied means for the actual defence of the soft body is to 

 be seen in the endless modifications of the skeleton ; first, in the production of the 

 enclosing lattice-shells and projecting radial spines, but especially also in the very varied 

 structure of the individual parts of the skeleton, and in the special difi"erentiation of the 

 small appendicular organs which grow out from it (hairs, thorns, spines, scales, spathdlaj, 

 anchors, &c.). Finally "mimicry" possesses a considerable significance among the 

 difi'erent forms of adaptation which are to be observed in this class. 



223. Phosphorescence. — Many Eadiolarians shine in the dark, and their phos- 

 phorescence presents the same phenomena as that of other luminous marine organisms ; it 

 is increased by mechanical and chemical irritation, or renewed if already extinguished. 

 The light is sometimes greenish, sometimes yellowish, and appears generally (if not 

 always) to radiate from the intracapsular fatty spheres (§ 73). Thus these latter unite 

 several functions, inasmuch as they serve, firstly, as reserve stores of nutriment, secondly, 

 as hydrostatic apparatus, and thirdly, as luminous organs for the protection of the 

 Radiolaria ; jarobably the light acts by frightening other animals, for the phosphorescent 

 animals are provided with spines, nettle-cells, poison glands or other defensive weapons. 

 The production of the light depends probably, as in other phosphorescent organisms, upon 

 the slow oxidation of the fat-globules, which combine with active oxygen in the presence 

 of alkalis. Phosphorescence is very likely widely distributed among the Radiolaria. 



The shining of the Eadiolaria in the dark has been noticed by the earliest observers of the class 

 (see L. K 1, p. 163, L. K 16, p. 2, and L. N. 52, pp. 136-139). In the winter of 1859 I observed 

 the production of light in the case of many monozootic and polyzootic Eadiolaria, but inadvertently 

 omitted to record the fact in my Monograph. I made more accurate observations in the winter of 

 1866 at Lanzerote in the Canary Islands, and convinced myself that the light emanates from the 

 central capsule, and in particular from the fat-globules contained in it. In most Polycyttaria 

 (both Collosphserida and S p h aj r o z o i d a), v?hen each central capsule contains a large central 

 oil-globule the light radiates from it. In Collozoum scrpcntinuvi (PI. 3, figs. 2, 3) each cylindrical 

 central capsule contains a row of luminous spherules like a string of beads. In Alacorys friderici 

 (PI. 65, fig. 1) the four-lobed central capsule contains four shining points. Karl Brandt has recently 

 made more detailed communication on this point (L. N. 52, p. 137). 



224. Sensation. — The general irritability which we ascribe to all organisms, and as 

 the basis of which we regard the protoplasm, remains at an inferior stage of development in 

 the Radiolaria. For although they are subject to various stimuli, and certainly possess a 

 power of discrimination, special sensory organs are not differentiated; the peripheral 

 portions of the protoplasm, and especially the pseudopodia, rather act both as organs 

 of the difi'erent kinds of sensation and various modes of motion. That difierent 

 Radiolaria have attained different degrees of development in this respect may be seen 



