622 L- R- <^'ary, 



genesis scheint mir der Umstand entg'egen zu stehen, daß aus dem 

 Keimstocke nicht nur Eizellen, sondern auch andere Elemente (Wand- 

 zellen) gebildet werden." 



None of these investigators gave any attention to the questions 

 of the formation of polar bodies. Their arguments for or against a 

 parthenogenetic development of the germ cells are purely theoretical. 



In recent years a number of papers have appeared which deal 

 with the question of the character of the development of the germ 

 cells in the nurse generations, although none of them have been 

 strictly cytological in character. 



CoE (1896) in studying Fasciola (Dlstomuni) hepatica, — the form 

 on which Leuckakt had based his conclusions concerning partheno- 

 genesis in the Malacocotylea — was unable to find any maturation 

 divisions or polar bodies. He states, however, that the absence of 

 the formation of a polar body i. e. the division of a germ cell into 

 two unequal cells only one of which develops further, does not 

 necessarily weigh against the „Einatur" of the germ cell. He 

 would trace back the maturation process into the earlier history of 

 the germ cells where at some definite division a parent cell divides 

 into two cells, each of which is a definitive egg. He compares this 

 process to the development of spermatozoa, where all of the ultimate 

 cells become of the same size and character. This conclusion has, 

 of course, no observations for its support, and besides it is opposed 

 to all the known facts of oogenesis. 



Eeuss (1903) concluded as the result of his studies on Distomiim 

 duplicatum, that there was a true maturation of the germ cells 

 within the sporocyst of this species. His evidence was, however, 

 very fragmentary, consisting only in the fact that he found small 

 cells with coarsely granular, apparently degerating, nuclei attached 

 to the larger germ cells, before these began to segment. He figures 

 (fig. 12 and 13) what he considers to be a maturation division. 

 The only evidence in favor of this conclusion is, however, that there 

 is no small granular nucleus attached to the germ cell in which the 

 spindle occurs. This fact appears to be for him sufficient evidence 

 that the result of the mitosis figured would have been the cutting 

 ott' of a polar body — (one of the coarsely granular nuclei) — from 

 the large germ cell. 



Reuss figures three polar bodies as being the number usually 

 found. He states that they persist for a long time attached to the 

 egg: and it would seem from his figures of some of the later seg- 



