Ookinesis in CVrebratnlus Lacteus. 369 



With iron-hsematoxylin the middle piece of the si^ermatozoon in 

 the egg stains as deep as the head. In thoroughly extracted prepa- 

 rations, however, the centriole coiner into view very distinctly (PI. 

 II, Fig. 21). A somewhat advanced spermatozoon is represented 

 in Fig. 27 (PI. II) ; the middle piece is here rhomboidal. Fig. 28 

 (PI. II) shows the same section subjected to further, extraction. 

 The centriole has been brought out more clearly into view; the 

 outline of the middle piece has disapjieared. It is striking that a fine 

 radiation (non-fibrous rays) converging to the middle piece has 

 been brought to light by extraction. Wilson states that at the 

 formation of the s])erm-aster the r,adial arrangement of alveoles pre- 

 cedes the true rays ('90, ]). 13). The same preparation was re-stained 

 with rubin S ; the outline of the middle-piece was restored as it 

 had been seen before extraction. The next stage is shown in Figs. 

 29 and 30 (PL II). The vesicular nature of the middle-piece is 

 now more pronounced. The centriole is found at the same place 

 where it previously was. In case the germinal vesicle fails to fade 

 the spermatozoon remains at this stage (TIertwig, O. and P., '87, 

 p. 199; Wilson, '96, p. 149, '00, p. 201; Boveri, '02, p. 44). In 

 eggs in which the germinal vesicle has faded faint rays are next 

 seen around the middle-piece^" (PI. II, Fig. 31). Another sperm 

 of about the same stage is shown in Fig. 32 (PI. II). Here the 

 middle-piece has the outline of a pentagon. Further extracted, a 

 sharply-defined centriole with elongated rays was seen (PI. II, 

 Fig. 33). The outline of the middle-piece was restored by re-stain- 

 ing with rubin S. The next stage is represented in Fig. 34 (PI. 

 II). The tail had disap]ieared and the sperm-rays have increased 



therefore, seems to have developed for the purpose of piercing through the egg 

 membrane and of boring into the egg. Later the sperm-head (now sperm 

 nucleus) becomes vacuolated (PI. II. Fig. .30) and chromatin collects on the 

 walls. Then the chromatin assumes a sphere-like form, which soon breaks 

 up into the chromosomes. As the sperm-nucleus grows, the chromosomes dis- 

 appear as such, leaving behind a few chromatin nucleoli. 



'"I met with a few cases, in which the sperm-rays have developed before the 

 shortening of the head. Fig. 23 (PI. II) shows this abnormal case. One 

 notices that the sperm-rays centre in the centriole in the middle piece. Fig. 24 

 (PI. II) represents another rase, in which rays have preeoeiously formed and 

 the throwing-off of the middle iiiece vesicle has also taken place. 



