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



PHYSIOLOGICAL SECTION. 



Chapter VIL— VEGETATIVE FUNCTIONS. 



(§§ 201-217.) 



201. Mechanism of the Functions. — The vital phenomena of the Radiolaria 

 are dependent upon the mechanical functions of their unicellular body, and like 

 those of all other organisms, are to be referred to physical and chemical natural laws. 

 All processes which appear in the life of the Radiolaria are, therefore, ultimately to be 

 explained by the attraction and repulsion of the smallest particles, which compose the 

 different portions of their unicellular body ; and the sensation of pleasure or the 

 opposite is in its turn the exciting cause of these elementary movements. Many 

 adaptive arrangements in the Radiolarian organism may produce the a2:)pearance of 

 being the premeditated result of causes working towards an end (" zweckthatig," causce 

 finales), but as opposed to this deceptive appearance it must here be expressly stated 

 that these may be recognised in accordance with the developmental theory as the 

 necessary consequence of mechanical causes {causes efficientes). 



Our physiological acquaintance with the Eadiolaria has by no means progressed so far as our 

 morplwlogical, so that the incomplete communications which are placed here for the sake of complete- 

 ness must be regarded merely as preliminary fragments, not as fully elaborated results. Since my 

 recent investigations have been mainly in the direction of morphology, I can add but little to the 

 physiological conclusions, which I stated at length in my monograph twenty-four years ago (L. N. 16, 

 pp. 12V-165). Eecently the vegetative physiology of the Eadiolaria has been much advanced by 

 the recognition of the symbiosis with the Xanthella3 (§ 205, L. N. 22, 39, 42). In addition Karl 

 Brandt has recently (1885) published several important contributions to the physiology of the 

 Polycyttaria or Sphaerozoea (L. N. 52). 



202. Distribution of Functions. — The distribution of the functions among the 

 various parts of the unicellular organism of the Radiolaria corresponds directly to their 

 anatomical composition, so that physiologically as well as morphologically the central 

 capsule and the extracapsulum appear as the two coordinated main components. On 

 the one hand the central capsule with its endoplasm and enclosed nucleus is the 

 central organ of the " cell-soul " (Zellseele), the unit regulating its animal and vegetative 

 functions, and the special organ of reproduction and inheritance. The extracapsulum 

 forms, on the other hand, by its calymma the protective envelope of the central 



