REPRODUCTION 247 



parasite servino; for the passage of food (Leger). An extreme case 

 of gregarine difl'ereiitiation has l>een described by Drzewiecki in 

 Stoniatophora coronata in which mouth, peristome and anus are said 

 to occur. (Reference from Doflein, 1916.) 



The buds of Suctoria have a rather complicated developmental 

 history, especially in forms whose ''embryos" are parasitic in other 

 Protozoa (Sphcerophrya species). The buds possess cilia which are 

 arranged in different patterns in the various species, and by which 

 they swim actively about until they finally settle down for develop- 

 ment. They also possess, as a rule, some longer cilia at the anterior 

 end which have been homologized with the adoral zone of the ciliated 

 Infusoria, and at the posterior end they possess a sucking disc by 

 means of which the buds attach themselves to some solid object 

 either living or lifeless, and from which a stalk is developed. With 

 growth of the stalk the cilia are absorbed and tentacles— suctorial, 

 piercing or seizing— are developed. In the parasitic forms the cili- 

 ated embryos may develop tentacles while in the motile condition, 

 but on coming in contact with a quondam host, cilia and tentacles 

 are absorbed and as an ectoparasite the young form makes a pit 

 in the cortex of the host. It may then reproduce by cell division 

 in this pit initil as many as 50 or more are produced, and these 

 escape through a slit-like birth opening of the improvised brood 

 pouch. 



In some types of Protozoa finally, especially in the colonial 

 flagellated forms, the single cell undergoes a series of cleavage 

 stages the sequence of which is similar to that of many types of eggs 

 of Metazoa. This is particularly striking in forms like Gonium 

 pectorale, Plaiydorina candata, StephanosphcBra plimalis, etc., which, 

 as adults, consist of definite numbers of cells arranged in definite 

 patterns (Fig. 3, p. 21). 



SPECIAL BIBLIOGRAPHY. 



Calkins, G. N.: 1911, Regeneration and Cell Division in Uronychia, Jour. Exper. 



Zool., vol. 10. 1919, Uroleptus mohilis 1: History of the Nuclei during Division 



and Conjugation, Jour. Exper. Zool., vol. 27, No. 3. 

 Child, C. M.: 1916, Age Cycles and Periodicities in Organisms, Proc. Am. Phil. 



Soc, vol. 55, No. 5. 

 Collin, D.: 1911, Etude monographique sur les acinetiens. Arch, zool exp. et gen., 



vol. 8. 

 Hartmann, M.: 1924, Der Ersatz der Fortpflanzung von Amoben durch fort- 



gesetzte Regeuerationen, Arch. Prot., vol. 49. 

 Janicki, C: 1910, Untersuchimgen an parasitischcn Flagellaten 1, Ztschr. wiss. 



Zool., vol. 95. 1915, Ibid., vof. 112. 

 MiNCHiN, E. A., and Thompson, J. D.: 1915, The Rat Trypanosoma, Trypanosoma 



lewisi and Its Relation to the Rat Flea Ceratophyllus fasciatus, Quart. Jour. 



Micr. Sci., vol. 60, Pt. 4. 

 Peebles, F.: 1912, Regeneration and Regulation in Paramecium caudatum, Biol. 



Bull. 

 W'allengren, H.: 1900, Zur Kenntnis der vergleichende Morphologic der hypo- 



trichcn Infusnrien, Bih. t. k. Svenska vet. Akad. Hand. vol. 26. 

 Wilson, E. B.: 1923, The Physical Basis of Life, New Haven, Yale Univ. Press. 



