1919] Boeck: Studies on Giardia Microti 121 



comet (pi. 1, figs. 1, 4, 5, 13, 15, 16), or they may appear as conglo- 

 merations of a material, cloud-like in character through the cytoplasm. 

 Such was the condition of the parabasal bodies during multiple fission 

 in G. muris (Kofoid and Christiansen, 1915). 



During mitosis in the free state of G. microti the parabasal bodies 

 are always present in the stages of the prophase and in the metaphase, 

 but they were often lacking in the anaphase and telophase and 

 almost without exception they are missing in the stages of plasmotomy. 

 The only exception was an instance described in which a parabasal 

 body was seen in one of the daughter flagellates in the process of 

 plasmotomy of a two-zooid somatella in the free state (Boeck, 1917). 

 In the investigations upon G. muris during mitosis the parabasal 

 bodies were absent in the late phases of mitosis and always absent in 

 the two-zooid somatellas resulting from binary fission (Kofoid and 

 Christiansen, 1915). Likewise in the four-zooid somatella resulting 

 from multiple fission of a flagellate in the free state, the parabasal 

 bodies were lacking. 



With the encystment of G. microti the parabasal bodies hyper- 

 trophy to a great extent (pi. 1, fig. 1) and as the process of binary 

 fission within the cyst continues the bodies disappear (pi. 1, figs. 6-8). 

 In multiple fission within the cyst of G. microti, there also occurs an 

 increase in size of the parabasal bodies (pi. 1, fig. 9), and when the 

 sixteen nuclei have been formed in many cases the parabasal bodies 

 are absent or they appear faint (pi. 1, fig. 11). The somatella stages 

 found in a free state may have resulted from their liberation from a 

 cyst by the digesting away of the cyst wall, and in these stages, it 

 has been pointed out, the parabasal bodies have disappeared. 



It was on these morphological aspects of the parabasal bodies dur- 

 ing mitosis and during encystment that the conclusion was reached 

 that these bodies were reserve food centers to be utilized during periods 

 of reproduction and during encystment, when the original source of 

 food supply had been cut off. At such periods as these there is an 

 extra drain on the food supply of the flagellate, since the rate of 

 metabolism during reproductive activity is great, and since during 

 encystment not only are reproductive processes carried on, necessitating 

 a drain on the food supply, but also encystment itself may extend over 

 a long period of time, which necessitates an extra food supply. This 

 food reserve is depleted at the end of encystment, when, for the most 

 part, the reproductive processes within have also been completed. 



