among this form, which starts with the appearance of the approach of 

 maturity, continues until the very death of the wornns. The free -swinaming 

 larvae emerge from these eggs after approximately 15to 20 days because 

 at that time the temperature conditions in the body of water are more favor- 

 able. The larvae of the gill forms, just as the larvae of P. integerrimum 

 from the urinary bladder, attach to the gills of the tadpoles. Their further 

 fate is the same as that of the larvae of P. integerrimum of the urinary 



bladder which settled on the gills of 

 older tadpoles . Morphological 

 differences between both are absent, 



Fig. 127. Polystoma integerrimum 

 Froelich, mature gill form from the 

 gills of tadpoles of Rana temporaria 

 L. from Peterhof (Leningrad region). 

 Natural size 1. 2 mm. 



Fig. 128. Polystoma integerrimum , 

 Froelich, young immature worm 

 from the urinary bladder of year and 

 one -half old Rajia temporaria L. 

 from Peterhof (Leningrad region). 

 Natural size 1. 5 mm. 



p. 125 



and during the metamorphosis of the tadpoles they pass from the gills 

 through the entire intestinal canal into the urinary bladder. In the urinary 

 bladder and sometimes somewhat earlier, the larvae begin gradually to 

 acquire the final structure of the attaching disc, which toward winter be- 

 comes fully formed with all three pairs of suckers and with a middle pair 

 of chitinous hooks. Further growth of Polystoma takes place during the 

 following summer and finally they reach maturity in the third year. It 

 must be indicated that the first maturity takes place with the presence of 

 an ovary of different form than among four -year-old worms and with testes 

 of smaller sizes. The deposition of young mature individuals of the urinary 

 bladder takes place just as among older ones but begins somewhat later and the 

 number of eggs deposited is smaller. 



130 



