1883-84-] Edinburgh Naturalists Field Club. 177 



' Monats. Akad. Wiss. Berlin '), adopted the parasitic view taken up 

 by Cienkowski, for the following reasons : — 



(«) The yellow cells survive two months after the death of the 

 Eadiolarian host. 



ih) They agree in widely different families — e.^., in Eadiolarik 

 and some Actiniaj. 



(c) They appear first in the outer part of the colony of Collozoum, 

 and gradually make their way inwards. 



{d) Their nuclei stain more deeply with carmine than liadiolarian 

 nuclei. 



(e) Their limiting membrane consists of cellulose, becoming blue 

 after treatment with an acid and iodine. 



(/) All yellow cells have a chlorophyll-like pigment nucleus and. 

 a starch-like product of assimilation, that assimilation product being 

 of two kinds — either (a) starchy, vacuolated, colourless, or pale-blue 

 granules, coloured violet or blue-violet by iodine, and not doubly 

 refractive; or (,S), compact, irregular, reddish or violet, doubly re- 

 fractive granules, upon which iodine produces no change — (Brandt 

 in Pfluger's 'Archiv.,' 1883). 



(7) Mr Geddes (' Proc. Ptoy. Soc. of Edin.,' 1881-82, pp. 382, 

 383) has stated, the subjoined grounds for regarding the yellow cells 

 of Eadiolarians as algoid in their nature : — ■ 



(a) They survive in dead Eadiolarians, and have encysted and 

 anueboid states. 



(i) Their mode of division is algoid. 



(c) Starch is present in them, as noted by Haeckel. 



(d) Their cell walls consist of true cellulose, as made out by first 

 preserving the animal in alcohol, then macerating for some hours in 

 weak KHO, which is thereafter neutralised by weak acetic acid, and 

 finally treating with weak iodine and strong H.^SO^. 



(e) Their yellow colour becomes green on treatment with alcohol, 

 and is identical with the pigment of Diatoms. 



(/) There is a copious evolution of oxygen during sunshine, as 

 referred to below. 



Brandt has named these parasitic yellow algoid-cells Zoozanthella, 

 and has asserted that they represent the resting-stages of various 

 marine Alga3, belonging chiefly to the class Melanophycefe (' Mt. 

 Zool. Stat. Neapel.,''l883); and again (Pfluger's 'Archiv.,' 1883), 

 that " if large quantities of the green cells be treated with filtered 

 water, they usually become zoospores provided with two cilia ante- 

 riorly, having their pigments arranged in parietal plates, and possess- 

 ing starch in their interior." 



As bearing on the important physiological inferences that are to be 

 drawn from such cases of consortism, the experiments of Geddes on 

 the evolution of oxygen in sunshine are very valuable. They are as 

 follows : — 



