ir. SPOBOZOA: COCCI DI^^. 215 



anchorage, and is lost when the animal gives np its connexion 

 with the host cell. Among the intestinal gregarinos frequently 

 occur 'associations' where two or more animals are fastened to- 

 gether head to tail in a row. Perhaps these associations are prep- 

 arations for conjugation which occurs in development. 



Reproduction occurs exclusively in an encysted condition (fig. 

 155, II, A). Usually two animals (sometimes one, rarely more than 

 two) occur in a cyst. A fusion of the two encysted animals does 

 not take place, but it is probable that a nuclear exchange (recalling 

 that of ciliates) takes place. After each individual has become 

 polynucleate by division of its nucleus, it divides at first super- 

 ficially, later internally into small particles, the sporoblasts (II, B), 

 which change into spores, here called pseudonavicella3. The 

 psoudonavicellas are mononucleate bodies with firm membrane and 

 usually sj^indle form in shape (III, AA). In these processes a 

 part of the gregarine takes no part. This residual body aiopears 

 under projoer conditions to swell ujj and rupture the cyst, thus 

 freeing the pseudonavicellas. In many gregarines there are sporo- 

 ducts for the escape of the pseudonavicellas (fig. 154, A). The 

 contents of the pseudonavicellas divides into (usually eight) sporo- 

 zoites or falciform spores which must jjass out from the spores and 

 into the cells of the host in order to form gregarines. This escajoe 

 of the sporozoites dejoends upon entrance into the proj)er host. 

 Often the transformation of the contents of the cysts into pseudo- 

 navicellas takes place when the cysts have left the original host. 



Best known are the 2Ionooystiste7iaxot the spermatheoa of earthworms, 

 and Gregarina (Clepsidrina) blattanim of the cockroach. The American 

 species have scarcely been touched. One species is abundant in the intes- 

 tine of Qeopliilus. 



Order II. Coccidiae. 

 The gregarines of all Sporozoa are nearest the Goccidim, which 

 are also cell parasites with a single nticlcus, but without cither cell 

 membrane or division into protomerite and detitomerite. In most 

 species, as in Coccidium euniculi, there are two types of reproduc- 

 tion, an endogenous, leading to ' autoinfection,' and an exogenous, 

 concerned in the transfer of the germs to other hosts. In the 

 first (lacking in many sj^ecies) the Corcidinin divides int(j many 

 falciform germs w"hich separate from each other and, witliont 

 alternation of hosts, enter other cells. The second type is begun 

 by fertilization. Certain individuals, by rapid division form 

 microgametes, small bodies swimming with serpentine motions or 

 bv one or two flagella. Other individuals do not divide, bi;t form 



