THE LICHEN AS TRANSMIGRANT 11 



by-product or reserve, including Foraminifera (Orbitolitcs, Globi- 

 gerina), Radiolaria, Flagellates, Ciliates (Vorticella), Sponges, 

 Hydrozoa, Anthozoa, Ctenophora, Echinodermata, Polyzoa, Venues 

 (C'onvoluta, Eunice), Tunicata and Mollusca, with reference only to 

 intrusive flagellated or otherwise simple protoplasts of an order very 

 comparable with the ' gonidia ' of a Lichen. The case of the Arthropod, 

 with more or less chitinous or calcified exoskeleton, and that of the 

 Vertebrate with similar exoskeletal armour, are alone omitted from 

 the list. For example, among Radiolaria, more than 100 species have 

 been described as containing ' yellow cells ' or Zooxanthelhe, of the 

 nature of Brown Flagellates (whether of Cryptomonadine or Peridine 

 nature), and such intrusive 'algal' zoids, invading the animal plasma, 

 lead on to endophytic and parasitic modes of existence. The photo- 

 synthetic intruder clearly gains shelter and a quiet medium ; and in 

 the case of a holozoic host in which metabolic waste may be 

 predominantly nitrogenous, a definite reason is established for such 

 invasion by algal zoids, in a medium in which scarcity of ions of 

 combined nitrogen is a limiting factor, as a ready solution of the 

 nitrogen-problem. The mechanism of such intrusion may be readily 

 ascribed to chemotactic action, as opposed to simple mechanical 

 intrusion by germinating zoids with rhizoid processes, seeking 

 attachment. 



As examples of symbiotic association in which photosynthesis is 

 apparently non-essential, may be instanced, even in the Plankton - 

 phase of the sea, cases as that of the autotrophic Silicofiagellate 

 Disteplutnus speculum, occurring in the calymna or outer plasmatic 

 layer of the Radiolarian Plieodaria which has no siliceous skeleton of 

 its own. The Plieodaria apparently collects living Disteplutnus and 

 utilizes it instead of spicules. Another Radiolarian, Aulocleptes, with 

 radial spicules only, utilizes Diatom-frustrules for tangential needles. 

 Free green algal units penetrate the mucilaginous sheath of Schizo- 

 nema Diatoms, giving almost the effect of lichen-gonidia ; and just as 

 Fungus parasites (Mycosplicerella) attack Helvetia and Ascopltyllum, 

 so Naviouloid Diatoms may be endophytic in the mucilage of the 

 receptacles of the latter. As amoebae and filamentous Bacteria may 

 live inside the sphere of Yolvox (Molisch), so a Cryptomonad is 

 described as living inside the sphere of PJ/ceocystis globosa (Scherffel). 

 Yellow cells or Zooxanthellse are described for Peridines as Pouchetia 

 and PolyJcrihos ; just as in turn Gymnodines maj r invade Copepod 

 eggs (Dogiel) and the alimentary canal of Copepods as Blastodinia 

 (Chatton). A good example of such simple association is afforded by 

 the Cryptomonad, C. Schaudinii, living and multiplying in great 

 profusion in the Milioline Foraminifer Peneroplis periitsus l of the 

 Mediterranean. The Cryptomonad invader is of much the same size 

 as the monokont gamete of the host, and the former are cleared out 

 of the plasma before gametes are matured. Infection takes place at 

 an early date, and the union suggests a simple case of parasitism. 

 Although the Cryptomonad units each possess a brown lamelliform 

 chloroplast, no special advantage to the host can be suggested when 



1 Winter (1907), Archiv Protist. Kund. x. p. 16. 



