176 Transactions of the [Sess. 



to the direct influence of sunlight, has demonstrated that oxygen gas 

 is evolved in large quantities (45 to 55 per cent), and that starch is 

 abundant in the green cells, so that the action is equivalent to that 

 of vegetable chlorophyll; while he has also given reasons for believing 

 that, in cases of consortism, we have illustrations of an ideal, complex 

 existence on the lines of mutual or reciprocal physiological accommo- 

 dation. L. Macchiati, too ('Bull. Soc. Entomol. Ital.,' 1883), has 

 asserted that certain Aphides (Siphonophora malvse and S. rosfe) lose 

 their colour when subjected to darkness, and believes that this 

 coloration is due to chlorophyll, although its physiological action re- 

 mains as yet undetermined. 



It is not necessary, however, that Algae thus associated with animals 

 should be green. It is well known that the green colour of chloro- 

 phyll is often masked by other hues present in the cells, producing, 

 for example, such shades as the brown of Diatomaceae, or the olive 

 of Fuci and Laminarias, or again the red of Florideae. So we find in 

 marine Sponges bluish-green Oscillatorice, and in Eadiolaria certain 

 yelloAv bodies of ovoid outline, which Prof. Huxley first named 

 " yellow cells." The views that have been held regarding these 

 yellow cells may be summarised as follows : — - 



(1) Johannes Mliller believed that they were concerned with the 

 reproduction of the Eadiolarians — a conception which he subsequently 

 abandoned. 



(2) Haeckel ('Die Eadiolarien,' p. 136) maintained that they 

 represented the liver cells of the simple saccular liver of Amphioxus, 

 and were accordingly functionally secretory cells, or simple digestive 

 glands ; but at a later period they were found to contain starch, and 

 he thereupon regarded them as related to the function of nutrition of 

 the Eadiolarians (' Amylum in d. gelben Zellen d. Eadiolarien,' Jena, 

 Zeitschrift 1870, p. 582). 



(3) Cienkowski, in 1871, enunciated the belief that they were 

 parasitic Algae, resting this view on the three considerations that their 

 number varies in the same species, and that after the death of the 

 Eadiolarian they are capable of multiplication, and of passing through 

 encysted and amoeboid phases. 



(4) Eichard Hertwig, in 1876, maintained that the yellow cells, 

 being developed from the protoplasm of the Eadiolarian, acted as 

 storehouses of reserve food material, as the starch in a Potato tuber, 

 as the albumen of a seed, or as the adipose tissue of an animal does ; 

 but in 1879, after observing that the yellow cells were absent in some 

 species, and that the origin of their nuclei from Eadiolarian nuclei 

 was improbable, he regarded them as parasitic Algae. 



(5) Huxley, in 1877 (' Anat. Invert. Anim.,' jx 90), speaking of 

 the same " oelleeform bodies," remarks that "the possibility that they 

 may be parasites must be borne in mind." 



(6) Dr Karl Brandt, in 1881 (" Untersuchungen an Eadiolarien," 



