organs, copulation, the act of deposition of eggs, and also 

 the structure of the ova at the time of maturation and 

 directly after deposition. 



The still-undeposited egg, hung in a special pocket 

 in the oviduct, consists of a fine-grained substance 

 (molecular bodies) and yolk (fatty bodies) ; it is provided 

 with a nucleus (embryonic vesicle) . Before the deposition, 

 the ovum, which is separated from the oviduct and is freely 

 situated in the egg-reservoir, has the same structure; the 

 nucleus already cannot be seen in a beam of light and can 

 be seen only during the crushing of the ovum. Later the 

 embryonic vesicle disappears completely. 



The second section of the work was devoted to the 

 description of embryonic development. In the deposited ovum 

 for one hour no change can be seen, and then at its poles 

 the following phenomena can be observed. At the beginning, 

 on one of them, a white spot appears; this increases and 

 turns into a disk with a grey spot in the center (Figure 36, a). 

 Then this grey center increases and a white spot appears in 

 it, and the external white disk is transformed into a ring, 

 which Grube called the polar ring (Figure 36, b) . The field 

 of formation of the polar ring he called the active pole, 

 since according to his observations, it is here at the time 

 of development of the embryo that the most noticeable changes 

 take place. On the opposite inactive pole a white ring appears, 

 but less distinctly delimited. The polar ring ascends over 

 the surface of the ovum in the form of a papilla, so that 

 after its infiltration its condensation can be prepared. 

 Grube considered that the formation of polar rings is the 

 result of the displacement of an internal substance, during 

 which the "molecular bodies" are gathered in the form of 

 rings on the poles. 



Following the appearance of polar rings, or, in Grube* s 

 expression, "the process of formation of fissures 

 (DURCHFURCHUNG) or, rather, cleft (ZERKLUFTUNG) . . . . 

 those fissures not only occur on the surface, but penetrate 

 deep into the mass of the yolk, as a simple experiment shows: 

 under careful pressure of the condensed yolk, it disintegrates 

 into as many parts as the segments are delimited by the 

 fissures" (p. 17). The first fissure divides the ovum into 



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