CHAPTER III 



THE GERM-CELL CYCLE IN THE P^DOGENETIC 

 FLY, MIASTOR 



THUS far in only one genus of animals has the 

 history of the germ cells from one generation to the 

 next been followed in detail through the entire 

 cycle. This is a genus of flies, Miastor, of the family 

 Cecidomyidae. One species, Miastor metraloas, oc- 

 curs in Europe and has there been studied especially 

 by Leuckart (1865), Metschnikoff (1865, 1866), and 

 Kahle (1908), and the only other species that has 

 been investigated is M. americana (Hegner, 1912, 

 1914a). 



Paedogenesis in Miastor was discovered by Wagner 

 in 1862, and was confirmed by Meinert in 1864. 

 In 1865 the first investigations of its embryological 

 development were published by Leuckart and Metsch- 

 nikoff. These were the earliest accounts of the 

 keimbahn in any animals. Only a glance at Metsch- 

 nikoff's report is necessary to convince one of the 

 favorableness of Miastor as material for germ-cell 

 studies. The primordial germ cell is shown to be 

 established at a very early period in the cleavage of 

 the egg, and the descendants of the primordial germ 

 cell are quite easily distinguishable from other cells 

 in the body even in in toto preparations. In spite of 



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