346 Kansas Academy of Science. 



pears in the solid sphere, the cells multiply rapidly and the embryo 

 becomes a blastula, S and T. The third stage in development, 

 shown in section in U, is that known as the gastrula, produced in 

 various ways, but usually by the invagination of one side of the 

 blastula, due to unequal cell division and growth. The gastrula 

 may be likened to a two- walled cup with a small mouth. In some 

 form or another all complex animals pass through this stage of de- 

 velopment, as well as the morula and blastula stages. After the 

 gastrula stage is reached animal bodies of the highest complexity 

 are produced by a series of simple and compound invaginations and 

 evaginations, tubular or furrow in shape and many times repeated, 

 involving the ectoderm, entoderm and mesoderm. 



SUMMARY OF REPRODUCTION IN PLANTS AND ANIMALS. 



T'and Z. — Diagram 1^ illustrates reproduction in animals, but 

 J^and Z are both required to illustrate the same in plants. It 

 should also be noted that in all cases when egg and sperm unite it 

 cannot be foretold whether the resulting individual will in the case 

 of animals produce eggs or sperms, or in the case of plants produce 

 spores that will develop into male or female gametophytes. 



For animals, in diagram Y, we will suppose that two sperms, 

 1, 1, unite with two eggs, 2, 2, each cell having a nucleus with 

 four chromosomes ; the resulting fertilized eggs, 3, 4, will each 

 have eight chromosomes. Let us suppose that the fertilized eggs 

 produce two individuals, one female, 3, 3, and one male, 4, 4. When 

 the female produces one functional egg, 5, and the male four func- 

 tional sperms, 6, B, 6, 6, the cycle will be complete. 



For phmts, in diagrams Y and Z, the process of reproduction is 

 the same as that indicated in diagram Y, except that one functional 

 spore capable of developing into a female gametophy te is produced, 



