THE MALMllA-UERM. 191 



of Cracow University, Eussia, whose results form the basis of tlie 

 following account*: 



The description of the life cycle may begin with the sporozoite, 

 or youngest form, of the gregarine parasite. This is a small, elongate 

 germ which makes its way through the fluids of the digestive tract of 

 Ciona to the epithelial cells which line that canal, (l^'ig. 1, A.) The 

 sporozoite penetrates one of these cells and begins to grow at the ex- 

 pense of the cell contents, until, finally, too large for the cell host, 

 it breaks the cell wall and falls into the lumen of the digestive tract, 

 where it soon attains its full size. (Fig. 1, B. C. D.) It is now a com- 

 paratively large, sac-like cell, swollen at one end, and with a distinct 

 nucleus. (Fig. 1, C.) After a longer or shorter period, not definitely 

 determined, two adult forms come together and pour out a sticky, fluid 

 substance, which soon hardens to form a common, firm covering, or 

 cyst. (Fig. 1, E.) Each nucleus then begins to divide, and, after a 

 multitude of daughter-nuclei have arisen, the protoplasm of the cell 

 breaks np into as many parts as there are nuclei (Fig. 1, F. G. H.). 

 These small protoplasmic parts (gametes) then wander out of the parent 

 membranes and ultimately fuse, two by two, while still remaining in 

 the original cj'st wall (Fig. 1, I. J.). After the fusion, the nucleus 

 and protoplasm in each double mass divides into eight parts, and a 

 firm, enveloping membrane is secreted about them. This spore-mem- 

 brane ultimately becomes impregnated with calcareous material, which 

 thus forms a firm and resisting capsule for the eight germs within. 

 Each germ is a sporozoite similar to the one which began the life cycle. 



During the process of sporozoite-formation, the parasite is passed 

 out with the fseces to the exterior. Here the original cyst ultimately 

 bursts and liberates the multitude of spores A\ith their contained 

 sporozoites. The latter are well protected, however, by their calcareous 

 shells, and do not suffer from the sea water or from drying. The 

 spores may be finally taken into the digestive tract with food, and with 

 this the opportunity for a renewed cycle is presented. The acids of 

 the digestive fluids dissolve the calcareous coverings, and the eight 

 sporozoites in each spore are liberated. The sporozoites again penetrate 

 the epithelial cells, grow to maturity and repeat the process indefinitely. 



In Coccidium, a parasite of some of the insects, the life history as 

 worked out by Dr. F. Schaudinn differs in one or two important points 

 from that of the gregarine. 



Sporozoites are formed as in the previous case, and these work their 

 way in a similar manner into the cells lining the digestive tract (Fig 3, 

 a). Unlike the gregarine, the main period of their life is passed in these 

 cells, and they drop into the lumen of the intestine only when they 



* Siedlicki. Uebei- die geschlechliche Vcrmehriing der ]\Ionocystis ascidiae 

 E. Lank. Bull. d. I'Acad. d. Sci. d. Cracovie, December, 1899. 



