In the conditions of the Leningrad region during the period 

 from 1927 to 1929, we observed the emergence of frogs from their places 

 of hibernation in the beginning of the third ten-day period of April and the 

 beginning of the deposition of roe by them (see Fig. 129) as early as the 

 25th to the 26th of April. The latter (deposition of roe, nobis) continues 

 usually for a long time, often until the end of the first ten days of May and 

 often the first tadpoles begin to appear by this time. Correspondingly, the 

 first copulating P. integerrimum were observed from the 22nd of April, 

 and the beginning of egg deposition from the 24th to the 25th. The deposition 

 of eggs by worms continues until the 10th to the 15th of May. The first 

 larvae usually appear on the gills of tadpoles from the 12th to the 15th of 

 May and adult gill forms are discovered from the first days of June at the 

 earliest and most often from the 10th to the 15th of June. The overgrowing 

 of the gills and metamorphosis of the tadpoles and consequently the death 

 of the "gill" P. integerrimum and the migration of the larvae into the 

 urinary bladder of the young frogs begins about the middle of July and 

 extends for 10 to 15 days, depending upon the peculiarities of the year. The 

 departure of the young frogs for hibernation and the cessation of growth of 

 young Polystoma until spring take place before the departure of the adult 

 frogs from hibernation (October) and in the main coincides with the cold 

 spells of the middle to the end of September. 



According to the data of Gallien, in France, (the region of the 

 Department of Vosges near the village of Hansel) the deposition of eggs by 

 P. integerrimum begins from the 25th of February and continues until the 

 25th of March with the maximum occurring about the 5th to the 15th of 

 March (see Fig. 130). The emergence of the larvae and the infection of the 

 tadpoles take place from the 15th of April to the 15th of May. The adult 

 gill forms appear from May 10th, and their egg deposition lasts until June 

 15th. The eggs of "gill" P. integerrimum develop in 20 to 25 days, and 

 the ones which were deposited after the first of June yield larvae which do 

 not find tadpoles suitable for infection (metamorphosis has already begun) 

 and for that reason are condemned to death. Correspondingly, according 

 to the data of some authors, the roe of the frog is deposited in March 

 mainly from the 15th to the 20th. The tadpoles emerge from the first days 

 of April and (continue, nobis) approximately uitil its second half. The 

 metamorphosis of the tadpoles begins from the 10th of June and basically 

 ends before the 20th. 



The difference between our data and those of Gallien consist 

 not only in the fact that all the processes observed by him take place earlier, 

 which is absolutely natural, but also in the fact that in our opinion some of 

 his statements are erroneous and demand verification. Thus, first of all 

 according to Gallien, the deposition of eggs of P, integerrimum in the 

 spring significantly precedes the deposition of roe by the frogs. As is 

 apparent from the data published by him, this difference consists of a 

 minimum of 15 days. Taking into consideration all ihe peculiarities of the 



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