The life historj' of Diplodiscus temporatus Stafford. 623 



mentation stages that he had counted the so-called "polar bodies" 

 as segmentation cells. 



Haswell (1903) noted the same sort of cells, "with deeply 

 staining- homogeneous nuclei", lying near the ovary "(Keimlager) in 

 the body cavity of the sporocyst of Echinostomum sp. He says in 

 regard to these cells: "If they are not to be regarded as of the 

 nature of polar bodies it seems difficult to account for them". 



Tennent (1906), in describing the development of the germ cells 

 in Bucephalus says: "The first appearence of activity in the germ 

 cell itself is the cutting ofi' of a small cell (fig. 15, b.) (As has 

 been already noted this may take place in the wall.) This cell 

 differs in appearence from the much larger germ cell in that its 

 nuclear contents are much more coarsely granular. These contents 

 in a later stage are seen gathered together into two masses, the 

 larger nucleus of the germ cell having in the mean time moved to 

 the opposite periphery of the cell. In stages which I believe to be 

 still older, a second cell has made its appearence, and still later 

 there are three, two of which seem to be the result of the division 

 of the first cell (fig. 15, c.)." 



KossBACH (1906) points out the resemblance of the so-called 

 polar bodies of Reuss to the very young germ cells. He states that 

 he has never seen the formation of a polar body in any of the 

 material which he has studied, and expresses a doubt as to the 

 occurence of this phenomona in any of the eggs (germ cells) arising 

 in the nurse generations of Trematodes. He admits, however that 

 there is a possibility that maturation of the germ cells may occur. 

 "Obwohl es mir, gleich wie Coe am Miracidium, nicht geglückt ist, 

 bei Sporocysten und Eedien Richtungsspindeln festzustellen, so will 

 ich damit jedoch nicht behaupten, daß eine Reifung der Keimzellen 

 nun auch ausgeschlossen sei. Die Keimzellen haben ja ohne weiteres 

 eine große Ähnlichkeit mit Eizellen, neuerdings sind auch solche 

 Reifungserscheinungen von den Keimzellen der Dicyemiden, wo die 

 Verhältnisse sehr ähnlich liegen, durch Haktmann bekannt geworden. 

 Alles das spricht dafür, daß vielleicht auch die Keimzellen der 

 Ammen der digenetischen Trematoden eine solche vor ihrer Furchung 

 durchzumachen haben; wenn es mir selbst auch nicht gelang, eine 

 solche nachzuweisen, so mögen andere Forscher darin vielleicht 

 glücklicher sein! . , . Solange nicht gezeigt wird, daß diese Zellen 

 aus der Keimzelle vermittels einer Reifungsspindel hervorgehen, ist 

 es mir unmöglich die REuss'sche Auffassung anzuerkennen." 



41* 



