120 University of California Publications in Zoology U^ou 19 



THE PARABASAL BODIES OF GIARDIA MICROTI 



Introduction 



In many of the parasitic Protozoa the process of nutrition does 

 not always result in a growth of the cytoplasmic body, but instead 

 there may result the formation of bodies in the cytoplasm, which act 

 as reserve food materials. These bodies may be intimately connected 

 with the motor activity of the organism, especially with the meta- 

 bolic activity, in which case they will be used later during rapid 

 growth, during reproductive periods, or during encystment, when the 

 original source of nutrition is cut off. 



These bodies have been called metaplastic bodies because they result 

 from the metabolic activity of the organisms and are deposited in the 

 cytoplasm. Among these bodies may be cited the paramylum grains 

 of flagellates, the paraglycogen grains of gregarines and ciliates, the 

 plastinoid granules of coccidia, and the parabasal bodies of flagellates. 



Function of the Parabasal Bodies 



In a previous paper by the author (1917) a short account was 

 'given of the behavior of the parabasal bodies of Giardia microti. It 

 was pointed out then that these organs were metabolic reserve centers 

 of food materials, which acted as ''conveniences on the part of the 

 flagellate for coping with the intestinal medium in which it lives. 

 They appeared to be more intimately connected with the metabolic 

 activity of the parasite rather than its motor activity. '' 



This hypothesis was based only upon morphological aspects of 

 these bodies during encystment and during the life of the parasite in 

 the free state. For the sake of completeness the activity of these 

 parabasal bodies during encystment and in the free state of the flagel- 

 late may be reviewed. 



In the free-living adult (full-sized) flagellate there are two para- 

 basal bodies located in the posterior third of the body and lying dorsal 

 and usually across the axostyle. The bodies are usually elongate fusi- 

 form in shape. In the cyst the bodies may be two or more in number 

 and are greatly hypertrophied at the beginning of encystment. In 

 the cyst the bodies are located in various regions but always in the 

 posterior part of the body. They often spread out like the tail of a 



