82 THE INVERTEBRATA 



condensing at certain points, at each of which it forms a cellulose spo- 

 rangium, often stalked. In the sporangium is a capillitium of cellulose 

 threads and entangled in the capillitium are uninucleate, cellulose- 

 coated spores, whose formation is preceded by a reduction division. 

 When the sporangium is ripe it bursts and the spores are dissemin- 

 ated by wind, etc. In damp surroundings they open and liberate each 

 an amoebula which becomes a flagellula. The flagellulae perform 

 syngamy and the zygote again becomes an amoebula. The amoebulae 

 tend to fuse and form small plasmodia. By multiplication of their 

 nuclei the adults arise. 



Chondrioderma (Fig. 73). On bean stalks. 

 Badhamia. On fungi, especially Stereum. 



Plasmodiophora. In turnips, causing "finger-and-toe" disease. No 

 sporangia. Distribution by flagellulae in soil. 



Class SPOROZOA 



Protozoa which in the principal phase have no external organs of 

 locomotion or are amoeboid ; are parasitic, and nearly always at some 

 stage intracellular ; have no meganucleus ; and form after syngamy 

 large numbers of spores, which may be sporozoites or undivided 

 zygotes. 



The two subclasses, Telosporidia and Neosporidia, of this class 

 have little in common, and their association in classification is a 

 matter of convenience. 



Though upon analysis the type of life history characteristic of the 

 Telosporidia is found to differ profoundly from those of the Neo- 

 sporidia, all sporozoan life histories are complicated. Usually they 

 comprise all the phases indicated in the scheme on p. 32, though in 

 the Eugregarinaria (and perhaps in the Actinomyxidea) agamogony is 

 omitted. Each phase, moreover, is liable to be elaborated. The term 

 sporoblast is applied to certain stages in various life histories, but un- 

 fortunately the stages so named are not all comparable with one 

 another. In the Telosporidia it denotes either the zygote or the 

 products of the first of two successive multiple fissions whereby the 

 sporozoites and other spore-like stages often arise. In the Neosporidia 

 it denotes the syncytia (of different origins in different groups) from 

 which by differentiation of cells complex spores are formed. 



Subclass TELOSPORIDIA 



Sporozoa in which the adult of the vegetative stage has only one 

 nucleus; and comes to an end with spore formation; and the spore 

 cases, if present, are simple structures, which nearly always contain 

 several sporozoites. 



