328 THE PROTOZOA 



of the nuclear membrane (Dogiel, 605) ; as a rule the surface of the nucleus 

 is perfectly smooth. 



Chromidia are stated to occur in the cytoplasm of some gregarines (compare 

 Kuschakewitsch). According to Comes, they are scarce in normal individuals, 

 but become abundant with over-nutrition ; since he states, however, that 

 they arise in the cytoplasm, it is possible that they represent grains of the 

 nature of volutin rather than true chromidia. According to Drzewccki, 

 however, the nucleus of Monocystids may, during the early growth of the 

 trophozoite, break up into chromidia and be re-formed again, or may throw 

 out vegetative chromidia which are absorbed in the cytoplasm ; Kuschake- 

 witsch, however, regards this as a degenerative process. 



Drzewecki affirms that Stomatophora (Monocystis) coronata, from the vesiculre 

 seminales of Pheretima sp., possesses a mouth-opening in a peristome, and an 

 anal aperture, and takes up solid food in the form of the spermatozoa of its 

 host. If so it is quite unique, not only among gregarines, but among Sporozoa 

 generally. The ingested spermatozoa are stated to be taken up and digested 

 by the nucleolus (karyosome). According to Hesse, the supposed mouth and 

 peristome are parts of a sucker-like organ of attachment. The alleged 

 nucleolar digestion is perhaps a misinterpretation of the extrusion of chroma- 

 tinic particles from the karyosome. 



The Gregarines are subdivided at the present time into two 

 suborders characterized by differences in the life-cycle. In the 

 first suborder, known as the Eugregarinse, the parasite has no 

 multiplicative phase, but the trophozoites proceed always as 

 sporonts to the propagative phase by a method of reproduction 

 (sporogony) which is combined with sexual processes, and leads 

 to the formation of resistant spores. In the second suborder, the 

 Schizogregarinse, the trophozoites which arise from the sporozoites 

 become schizonts which multiply for several generations non-sexually, 

 by schizogony, before a generation of sporonts (gamonts or gameto- 

 cytes) is produced which proceed to reproduce themselves by sexual 

 sporogony. Stated briefly, the Eugregarinse have only a propaga- 

 tive phase, sporogony, in their life-cycle ; the Schizogregarinae have 

 both a multiplicative phase, schizogony, and sporogony. The 

 sporogony is of essentially the same type in both orders. It is 

 simplest, therefore, first to describe the life-cycle of a eugregarine, 

 and then to deal with the multiplicative phases of the schizogre- 

 garine. The complete life-cycle of a eugregarine may be divided 

 into eight phases. 



1. The sporozoites are liberated from the spores in the digestive 

 tract of the host in all cases known, and usually proceed at once to 

 attach themselves to, or penetrate into, the cells of the lining 

 epithelium of the gut ; but in a few cases the sporozoites pass through 

 the wall of the gut into other organs, as does, for example, the 

 common Monocystis of the earthworm, which penetrates into the 

 vesicula seminalis, and finally into sperm-cells. 



2. In the early cytozoic phase the trophozoite may be con- 

 tained completely within a cell (Fig. 143, A, B,) or merely attached 

 to it; the former condition, speaking generally, is characteristic 



