XIII, D, 5 Haughwout: Protozoa of Manila and Vicinity: I 179 



Without entering into the details of this most interesting con- 

 troversy, it may be said that there is abundant reason to believe 

 that protozoa undergo physiological old age in common with 

 other animals. The waning vitality, which accompanies this 

 phenomenon, is restored and the animal rejuvenated by a process 

 of fertilization, or, as it is frequently called, syngamy, which is 

 probably of universal occurrence among the Protozoa. Funda- 

 mentally it seems to make little difference whether this process 

 is one of autogamy, endogamy, exogamy, endomixis, or parthe- 

 nogenesis. In every case the need for fertilization asserts itself 

 ultimately and is met in some fashion, primitive or complex, 

 and forms a most interesting stage in the life cycle of the 

 protozoon. It should be borne in mind, however, that endomixis 

 is merely a process of nuclear reorganization unaccompanied 

 by synkaryon formation. 



These, then, constitute the facts that are collectively known as 

 the life cycle. 



The study of the Protozoa is, therefore, seen to involve a 

 study of morphology, physiology, and cytology with all their 

 ramifications, which has led Calkins * to define protozoology — 



as that branch of the biological sciences which deals with the application 

 of biological problems to, and with search for their solution in, the lowest 

 group of animal organisms — the Protozoa. 



The literature on the Protozoa is vast and is scattered through 

 many publications. There are several textbooks and innumer- 

 able papers 'and monographs. The literature is found in the 

 journals of zoology, botany, medicine, sanitation and hygiene, 

 pathology and bacteriology, physiology and pharmacology, chem- 

 istry, genetics, anatomy, and occasionally in other scientific and 

 semiscientific journals. At the end of this paper is appended 

 a short list of some of the standard works on protozoology, which 

 will be of aid to the student in the identification of species 

 hitherto unreported in the Philippine Islands. No extended 

 study of the world distribution of the Protozoa has been as yet 

 undertaken, but for the most part they seem quite cosmopolitan, 

 and I have found few fresh-water protozoa in the Philippines 

 that were not familiar to me in the United States. 



Collection. — The amateur collector will probably make his 

 studies on forms collected at random. Really systematic work, 

 however, entails a study of the ecology of the protozoa sought 

 and a knowledge of the physical and chemical conditions in the 



* Calkins, G. N., The scope of protozoology, Science (1911), n. s. 34, 129. 



