FERTILIZATION AND MITOSIS 1 



1. Examine, with the low and the high power, a prepared transverse 

 section of the uterus of Ascaris. Note the heavy uterine wall and the 

 central lumen containing many thick-shelled eggs which are in various 

 stages of mitosis. Draw the entire section of the uterus in outline and 

 then fill in a sector to show the details. 



2. Study the preparation with the high power. Identify eggs in the 

 following stages of fertilization and mitosis and make a drawing of each 

 stage about two inches in diameter : 



(a) Contact and fusion of the male and female gametic nuclei, 

 which constitutes the essential feature of fertilization, and is followed 

 by the various stages of mitosis. 



(6) Early prophase, with the chromatin in each gametic nucleus in 

 the form of a long thread (spireme), and the centrosomes at opposite poles 

 of the fusion nucleus (synkaryon). 



(c) Late prophase, with the chromatin in the form of definite chro- 

 mosomes, the nuclear membranes broken down, and the spindle well- 

 developed. 



(d) Metaphase, with the chromosomes divided in the equatorial 

 plate; or the slightly later anaphase, with the chromosomes leaving 

 the equatorial plate and moving along the spindle fibers toward the cen- 

 trosomes. 



(e) Telophase, with the spindle breaking down and the cytoplasm of 

 the cell dividing to form two cells. 



Label in each of the above stages where present : egg shell, cyto- 

 plasm, CENTROSOMES, ASTERS, SPINDLE FIRERS, and CHROMATIN, Or 

 CHROMOSOMES. 



3. The process of mitosis may also be studied in permanent prepara- 

 tions of the Onion root tip (page 247) which have been properly stained. 

 Study the stages corresponding to those described under (6), (c), (d), and 

 (e) of the preceding paragraph and make a series of drawings which will 

 show all details of the process which you have been able to observe. 



i B. pp. 222-223. 



357 



