FIRST STAGE: For this stage, characteristic phenomena 

 are taking place in the above mentioned light spot, which, 

 in Warnek's words, occupies the place of the rudimentary 

 (embryonic) vesicle. This spot is in the beginning completely 

 round (Figure 39, 3), then becomes elongated and subsequently 

 takes the form of a biscuit and the shape of a figure eight 

 (Figure 39, 4 and 5). After that when the spot (i.e. nucleus) 

 is twisted by the means just described, it comes nearer to a 

 certain region of the periphery of the yolk (ovum) . The end 

 of the spot which is turned to the surface of the yolk widens, 

 and it acquires the form of a blunt rounded cone, in addition 

 between the outer area of this cone and the membrane of the 

 yolk a transparent crescent-shaped region appears (Figure 39, 

 7) . From this crescent-shaped region two small vesicles become 

 separated, which, being isolated from the ovum, remain near it 

 throughout the following development. The place of deviation 

 of these vesicles becomes the center of formation of fissures, 

 later dividing the yolk into two, then into four parts. 



The separation of the vesicles Warnek described as 

 follows: on the external surface of the crescent-shaped region 

 a small elevation appears under the yolk membrane. It 

 gradually enlarges, acquiring the form of a spherical segment, 

 a hemisphere, then a complete globule, which is set on a 

 sufficiently thick stalk. Then this stalk becomes unlaced, 

 and the globule becomes free (Figure 39, 9). After the 

 formation of one vesicle the second one appears exactly as 

 the first (Figure 39, 9 and 10). Thus, in Warnek's observa- 

 tions, the crescent-shaped region separates the forming 

 vesicles from the light spot (i.e. from both nuclei of the 

 ovum) . He concluded that the nucleus does not share in the 

 formation, at least, of the external vesicles. He made this 

 erroneous conclusion because the intravital observations which 

 Warnek used did not suggest tracing the processes taking 

 place in the nucleus. From this came the further erroneous 

 claim that the separating vesicles could not be regarded as 

 the vesicles of Purkinje or its remnants. In accordance with 

 this assertion Warnek refused to recognize for the vesicles 

 separated from the ovum that important role claimed for them 

 by many authors, and he objected to the name "directing 

 vesicle" {vesioula directrix') . Warnek did not like this 

 name as it returned embryologists to the time when they 

 believed in an Archean spirit directing vital phenomena. 



546 



