George W. Bartelmez 5r 



the yolk within the oviduct there was no trace of the genninal vesicle, 

 although at the beginning, while it was still clinging to the infundib- 

 ulum, the remains of the colliculus were present, easily separable 

 from the yolk. So it ai)pears that the vesicle is burst or dissolved by 

 contractions of the oviduct when the semi-fluid yolk is taken up by 

 the infundibulum and that its fluid is so mixed with the substance 

 of the colliculus that from it that fluid [colliquamenliim] with white 

 granules is produced; from the rest of the colliculus, the nucleus [of 

 Pander] is formed.* 



§3 



On the development of the 



germinal vesicle (Keimbldschen). 



[^ 5 ] The next job was to investigate this same vesicle in the cicatriculae 



of still smaller eggs, an easy matter, especially in cases where the yolk 

 material has not yet attained the usual density and flows like milk. 

 Then when the ovum is cut open under water, the membrane is 

 promptly freed of yolk. On its inner surface a diaphanous vesicle pro- 

 trudes slightly, surrounded by a narrow halo of white globular mate- 

 rial, which in the mature ovum constitutes the cumulus. At this stage 

 the vitelline membrane is of the softest texture and is covered with a 

 rather thick layer of globules. The vesicle does not increase in size 

 from the beginning to maturity in proportion to the egg as a whole. 

 In the smallest it is scarcely less than half the size it attains in mature 

 eggs, so that it then may fill almost all the space destined for the yolk. 

 If you were to look back over the course of development, you would 

 say that the vesicle is the first structure in the ovule to be stimulated 

 to germinate but at a slow rate which later and up to maturity is far 

 surpassed by the yolk and its envelopes, so that from the mathematical 

 point of view there are two series of equal length beginning with 

 equal volumes, one of them increases more slowly, the other more 

 rapidly, so that while the ratio is at first practically one of equality 

 they eventually differ from one another many thousand times in mag- 

 nitude. In ovules that have reached the diameter of one line and less, 

 a circular spot corresponding to the vesicle is to be seen from tiie ex- 

 terior under a lens of medium power, shadowed forth [from the yolk- 

 laden ooplasm] by its transparency [umbrosa ob pelluciditatem] (figs. 

 12-15). It is easily detected in ovules of 4 to 6 lines where it stands 

 out immediately when the membranes are cut open under water and 

 the vitelline membrane is removed. Here I must call attention to 



* [This note was added in the 1830 edition.] It now seems more probable to me 

 that the vesicle forms the basis of the dark central part of the blastoderm referred 

 to above (fig. 11) and that its hemisphere is expanded into a double membrane 

 [that is, the two-layered blastoderm]. 



