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J. P. Munson 
that it appears early and disappears late is very interesting in view of 
what we now know of this body. 
In the same year Cramer (20) saw in small eggs of the frog, a granulär 
body outside the germinal vesicle. This is what Cramer says: “In dem 
freien Raum hegt die kleine Kugel von Körnchen, die früher von der 
Dotterhaut eng umgeben war . . . Wird das Ei etwas größer, dann erweicht 
die kleine Kugel, und immer flüssiger werdend verbreiten sich die Massen 
in einem eleganten Halbmond in der Höhle des Dotterraums.” 
Two years later Carus (18) made similar observations on frog’s 
eggs; and comparing the body with the yolk nucleus of spiders, con- 
cluded that yolk is formed on its surface. In 1849, von Wittich (98) 
wrote: “In den Eiern einiger Arten tritt nun, wie ich es bereits in meiner 
Inaugural-Dissertation beschrieb, und wie auch seitdem v. Siebold beob- 
achtet hat, neben dem Keimbläschen noch ein zweiter eigentümlicher 
Körper auf, über dessen Entstehung ich in meiner Abhandlung eine aller- 
dings von Siebold’s Angabe abweichende Ansicht aussprach, bei der ich 
aber nach vielfältiger Beobachtung doch beharren zu müssen glaube.” 
Coste (19) is often quoted as having seen the yolk nucleus in birds 
in 1847. In his large work, he refers to the cicatricula in birds, reptiles, 
and fishes, but there are reasons for doubting that he had seen the real 
yolk nucleus. 
In 1853, Leuckart (49) referred to the yolk nucleus in his famous 
article “Zeugung” as a very variable body. “Die Bedeutung dieses Körpers 
ist unbekannt.” 
Writers often quote Burmeister (16) as having disc-overed the yolk 
nucleus in eggs of Brancliipus 1856. 1 have not succeeded in convincing 
mvself that he actuallv saw the yolk nucleus. 
Leydig (50) published a textbook on histology in 1857, in which he 
figured the yolk nucleus in Araehnids, with the eonfession that the mean- 
ing and use of this body is unknown to him. 
In the same year, 1861, that Max Schultze defined the cell as it has 
since been conceived, Gegenbaur (28) published his famous generaliza- 
tion that the egg is a cell. He, also, showed the presence of a yolk nucleus 
in the egg of birds. 
In 1861, too, Lubbock (55) claimed to have seen the yolk nucleus in 
eggs of several species of Myriapods. He compares it to the body discovered 
by v. Wittich for the first time in spiders. Because of its c-onstancy, he 
seems to believe that it ought to have some important funetion; but is 
unable to assign any. Of Lithobius he says: “When the egg has attained 
a eertain size, but bcfore it has begun to darken, a small vesicle, about 
