328 



BIOLOGY OF THE PROTOZOA 



Kranzlin and earlier, by himself, is only a ])hase in the degeneration 

 of nuclei many of which are disposed of in this way at this period. 

 Fertilization is exogamic, the gametes l)eing the myxamoebfv and 

 myxoflagellates which ultimately emerge from the spores. 



Liberation of the spores is accomplished in different ways. In 

 some cases a lid is raised off the sporangium; in others the peridium 

 dissolves in spots leaving a fenestrated capsule; in still others the 

 capsule splits longitudinally. The dry, powdery spores are distrib- 

 uted in various ways, air currents plaA'ing a conspicuous part, and 

 they finally germinate in the presence of moisture. Myxamoebse 

 and myxoflagellates are formed and the cycle is completed. 



Fig. 146. — Fruiting bodies of Coviatricha nigra. A, five stalked spore capsules- 

 B, section of cap.sule with columella, capillitium, and spores. (After MacBride.) 



Genera and species of Mycetozoa are distinguished according 

 to the nature of the plasmodia and hy the form and organization of 

 the sporangia. 



We follow Doflein in the main grouping of the sub-class Mycetozoa 

 but raise his sub-orders to the value of orders, as follows: 



Order I. Acrasida, van Tieghem.— In this group the fusion of 

 amoebse is incomplete but the organisms come together as a gregaloid 

 colony, which is termed here a pseudo-plasmodium. Myxamoeb^ 

 are present, but myxoflagellates are not formed. 



Order II. Phufomrixida, Schroter.— These are parasites in plants 

 and in insects; true j^lasmodia are formed but peridia and capillitia 

 are absent. Both myxamoehe and myxoflagellates are character- 

 istic. 



Order III. EuplasNKxUda, Lister.— Mycetozoa with myxamoeba^ 

 and myxoflagellates and with true ])lasm()dium formation by plasto- 

 gamic fusion of ama^buhe. The Order includes forms with the full 

 life history as described above. 



