GENERAL BIOLOGY 



2. Maturation and Fertilization. The last two cell divisions in 

 the oogenesis and spermatogenesis are known as the "maturation 

 divisions" and lead to the reduction of the chromosomes in the ma- 

 ture egg and sperm to half the usual number. When the egg is fer- 

 tilized the normal number is again restored. 



Carefully study the maturation and fertilization of the egg of 

 Ascaris megalocephala, with especial reference to the chromo- 

 somes. Observe that in the maturation of the egg (also of the 

 sperm) the number of chromosomes is reduced to two, and in the 

 union of the egg and sperm the number is increased to four, the 

 normal number. Draw eggs and sperm showing all of these points. 



3. Cleavage. Observe that in the cleavage of the egg of Ascaris 

 each chromosome is split longitudinally, so that each daughter 

 nucleus receives two chromosomes from the egg and two from 

 the sperm. Draw. 



Enumerate the evidences that the chromosomes contain the in- 

 heritance factors. 



III. COMBINATIONS OF SEXUAL AND ASEXUAL REPRODUCTION. 



1. Metagenesis. Alternation of asexual reproduction with sex- 

 ual, as in hydromedusae. 



2. Heterogeny. Alternation of monogonic reproduction with 

 amphigonic, as in fluke worms. 



IV. HEREDITY. Germinal likeness or variation as contrasted with 

 environmental. 



1. Mendelian (alternative) inheritance. Study and draw Mu- 

 seum exhibits illustrating this kind of inheritance. 



2. Give Mendelian formulas and ratios to the third filial genera- 

 tion (F 3 ) for the offspring of (a) two homozygous parents, (b) 

 two heterozygous parents, and (c) one homozygous and one hete- 

 rozygous parent. Explain sex as a Mendelian character and show 

 by formulas and ratios in which of these three groups it belongs. 



3. Describe any cases of inheritance, known to you, which 

 seem to be non-Mendelian, and show how they may be explained 

 in accordance with Mendelian principles. 



4. All members of the class are invited, but not required, to 

 fill out a Family Record blank, giving details of their own heredity 

 for the use of the Committee on Eugenics. 



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