422 BIOLOGY OF THE PROTOZOA 



Except for the main groups which will probabl.y persist, the classi- 

 fication of Telosporidia is not entirely satisfactory. We follow 

 Doflein in the main, making only such changes as are necessary in 

 raising Sporozoa to the grade of a sub-phylum instead of a class. 

 Here also, we include in an Appendix a group of forms which have 

 been sifted out of other groups of Protozoa or Bacteria, and included 

 with the Sporozoa largely because there seems to be no other place 

 to put them. 



Sub-class I. GREGARINIDA. 



The gregarines are typically coelozoic or lumen-dwelling parasites 

 of the invertebrates particularly of annelids and arthropods. They 

 vary in size from 10/x to 16 mm. (Porospora gigantea) and are prone 

 to collect in masses in the intestine, a gregarious habit from which 

 the name of the group is derived. Although saprozoic or osmotic 

 in nutrition they apparently do very little if any damage to the host 

 organism, differing in this respect from the intracellular Coccidio- 

 morpha. The most frequent site of parasitism is the digestive tract 

 and the glands opening into it {e. g., MalpigJiian tubules) but the 

 sporozoites of some forms penetrate the wall of the gut and enter 

 the body cavity where they form cysts on the coelomic side of the 

 intestinal wall or develop as free forms in the lumen of the seminal 

 vesicles (Monocystidse) or of other parts of the body cavity. 



Gregarines are widely varied in form as well as in size but so far 

 as the present accounts go they are similar in their protoplasmic 

 make-up. A peripheral outer layer of lifeless material forms the 

 epicyte which is equivalent to the pellicle or periplast of other 

 Protozoa. This is secreted by the ectoplasm and is frequently 

 drawn out into attaching organs in the form of filaments, hooks, 

 anchors and knobs. The outer surface is often definitely ribbed, 

 the ribs running longitudinally from end to end of the body. The 

 furrows between the ribs are filled with a gelatinous material derived 

 from a second layer also lifeless, of the cortex and termed by 

 Schewiakoff the gelatinous layer. Movement of gregarines accord- 

 ing to Schewiakoff is due to the secretion from the ectoplasm of this 

 gelatinous material which collects from the furrows at the posterior 

 end, hardens, and forms a resistant column against which continued 

 secretion pushes the organism forward. The third zone of the 

 body wall is formed by the living ectoplasm, which with the possible 

 exception of Stomatoyhora conmaia described b\' Hesse (1909) as 

 possessing a mouth, peristome and cell anus, forms an unbroken, 

 living, protoplasmic membrane. The endoplasm, or fourth zone 

 finally, forms the bulk of the organism and contains the single 

 nucleus usually provided with a large endosome. Paragl\'cogen, 

 volutin granules and other products of living activity make the endo- 

 plasm dense and homogenous so that it appears white by reflected 



