PHYSIOLOGY OF THE INVERTEBRATA. 405 



In the Grcfjarincv reproduction occurs by endogenous 

 division of the encysted body. Sometimes two full grown 

 organisms come together, adhere, and then surround them- 

 selves with a cyst. The result in each case is the forma- 

 tion of segments, wliich become spindle-shaped cells, called 

 pseudo-navicelke. These grow and finally rupture the cyst, 

 and thereby are set free. The pseudo-navicellte are sur- 

 rounded by cell- walls, but these burst, and the protoplasmic 

 contents of each escapes as a moner-like cell resembling 

 rrotamoiba. The moner now becomes differentiated into 

 ectosarc and endosarc, and the young Gregarina is now 

 amoebiform. In this stage of the development two arm-like 

 projections appear : one of these lengthens and separates, 

 forming a perfect Gregarina. The other eloa gates and absorbs 

 the rest of the mass and also becomes a perfect Gregarina. 

 This elongating stage has been termed by Van Beneden, the 

 pseudo-filaria phase. Afterwards the body becomes shorter 

 and broader, and a nucleus appears, the animal then passes 

 into the adult form. 



The Infusoria propagate by fission, endogenous division, 

 gemmation, and conjugation. 



In the Infusoria Jiagellata multiplication by longitudinal 

 fission occurs in several genera. For instance, in Codosiga, 

 the flagellum is first retracted and then fission takes place ; 

 in Antliopliysa the cell becomes encysted before the division 

 occurs. 



Drs. Dallinger and Drysdale have investigated the life- 

 cycle of many genera and species of the Infusoria Jiagellata. 

 ]\Iany of these forms multiply by — 



(ti) Fission (with or without encystment). 



(6) Conjugation. 



In the case of conjugation, the body which is formed 

 becomes encysted for a time, but ultimately the contents of 

 the cyst divide into either large or small bodies, which are 

 destined to assume the parental form. 



The complete life-history of Amj^hipleicra pellucula is 



