604 SUMMARY OF CURRENT RESEARCHES RELATINa TO 



to 4318 species, 3508 of wMcli are new. For a really complete examina- 

 tion the lifetime of one man would not suffice. 



The richest source of material was the Radiolarian ooze of the Pacific 

 Ocean ; the alimentary canal of aquatic animals, and the coprolites of the 

 Jurassic period were full of specimens. 



It will be useful to quote Prof. Hackel's definition of the Eadiolaria : — 

 " They are marine Ehizopoda, whose unicellular body always consists of 

 two main portions, separated by a membrane ; an inner central capsule 

 (with one or more nuclei), and an extracapsulum (the external calymma, 

 which has no nucleus and the pseudopodia) ; the endoplasm of the former 

 and the exoplasm of the latter are connected by openings in the capsule 

 membrane. The central capsule is partly the general central organ of the 

 Eadiolarian cell, partly the special organ of reproduction, since its intra- 

 capsular protoplasm, along with the nuclei imbedded in it, serves for the 

 formation of flagellate spores. The extracapsulum is partly the general 

 organ for intercourse with the outer world, partly the special organ of pro- 

 tection (calymma) and nutrition (sarcomatrix). The skeleton varies in 

 form and is generally composed of silica, sometimes of acanthin. The cell 

 usually leads an isolated existence (Monocyttaria), and only a small 

 minority of one legion are united in colonies (Polycyttaria)." 



The systematic catalogue is brought up to the year 1884, and contains 

 20 orders, 85 families, 739 genera, and 4318 species; this last is probably 

 not one-half the number of recent species ; two sub-classes may be estab- 

 lished, the first, that of the Porulosa or Holotrypasta, containing the forms 

 in which the central capsule is originally spherical, without osculum or 

 principal opening with innumerable fine pores ; the Osculosa or Mesotry- 

 pasta have the central capsule originally monaxid, with an osculum at the 

 basal pole of the vertical main axis ; each sub-class consists of two legions, 

 first of the Spumellaria (Peripylea) and Acantharia (Actipylea), the second 

 of the Nassellaria (Monopylea) and Phoeodaria (Cannopylea). It is among 

 the Spumellaria only that colonies are formed. 



The characteristic capsule-membrane is not to be compared with an 

 ordinary cell-membrane, but must be regarded as an internal dififerentiated 

 product ; the central capsule is regarded as the general central organ of the 

 " cell-soul " for the discharge of its sensory and motor functions (com- 

 parable to a ganglion cell), and is also the special organ of reproduction 

 (sporangium) ; it and the extracapsulum are to be regarded both morpho- 

 logically and physiologically as the two characteristic co-ordinated principal 

 parts of the unicellular Eadiolarian organism. Sixteen geometrical types 

 are recognized, and examples are given of each ; the central capsule itself 

 may belong to one of five well-marked different forms ; the nuclei may be 

 ellipsoidal, discoidal, stellate, amoeboid or lobate. After describing the 

 various secondary products which are also found within the capsule^ the 

 author passes to the extracapsulum which consists of the calymma or extra- 

 capsular jelly-veil, the sarcomatrix or layer of exoplasm immediately sur- 

 rounding the membrane of the central capsule, the sarcodictyum or network 

 of exoplasm, covering the surface of the calymma, and the pseudopodia or 

 radial fibres of exoplasm, which are discussed separately and in detail. 



In the fourth chapter the skeleton is elaborately dealt with ; it is a part 

 of the organism which is extremely well developed ; in this chapter only 

 the more important points are treated, the special differences being dealt 

 with in the systematic portion of the monograph. In the ontogenetic 

 development of the Eadiolaria an Astasia-stage is succeeded by an Actino- 

 phrys-Bta.ge, that by Sphserasirum, and that by the Actissa-stage, Actissa 

 being the prototype of the whole class. 



