Biological Papers. 345 



microspores always produce, on germination, male gametophytes> 

 and the megaspores female gametophytes. 



In the megasporangium (ovule) of the canna four megaspores 

 develop, according to the ancient instinct, but only one is func- 

 tional. In most angiosperms, including the cottonwood, only one 

 megaspore reaches any size. This megaspore, shown in P, con- 

 tains at first only one nucleus. This nucleus soon divides in rapid 

 succession till eight nuclei are formed, four at each end of the 

 megaspore or embryo-sac Then one of each four moves to the 

 middle of the sac and there the two fuse to make the polar nucleus, 

 P-^. Of the three nuclei which remain near the micropylar end 

 of the sac, 4 and 5 are synergids or helpers, and 1 functions as egg. 

 The three nuclei at the distal end of the sac are the antipodal 

 nuclei, 3, and are believed to represent a few of the cells of the de- 

 generate female gametophyte. Possibly the synergids, 4 and 5, 

 represent an archegoniuni. 



When the pollen (microspore) tube reaches the vicinity of the 

 embryo-sac, the tube nucleus, 6, disintegrates, and the mother 

 sperm nucleus divides into two sperms, 7 and 8. Synergid 4 dis- 

 appears and one sperm nucleus, 7, passes into the sac, makes its 

 way to the polar nucleus, 2, and unites with it, forming the endo- 

 sperm nucleus which has charge of providing nourishment for. the 

 embryo. Sperm nucleus 8 enters the sac and unites with the egg. 

 The fertilized egg at once takes nourishment and divides repeatedly. 

 True to an ancient instinct, it so divides at first as to make a fila- 

 ment, as is still the only or chief method of the algse. This fila- 

 ment, the suspensor, Q2, serves to push the rapidly growing 

 embryo, Q 3, into the food stored in the endosperm. ^-1 repre- 

 sents the location of the micropyle. How can any one compel his 

 mind, even though it be steeped in physics and chemistry — how 

 can any one believe that this wonderful process of fertilization and 

 development is merely a function of matter? 



DEVELOPMENT OF THE ANIMAL EGG. 



R to X. — The fertilized animal egg consists usually of a large 

 amount of cytoplasm, R-1, a nucleus which contains chromatin, 

 ^-2, which becomes organized into the normal number of chromo- 

 somes when the cell is preparing to divide, and a centrosome, 7?-3. 

 The fertilized egg-cell of animals divides and redivides in a fashion 

 peculiar to animals. The first divisions are in the three planes at 

 right angles to one another, X-1, 2, 3, making first two cells, V, four 

 cells, W, then eight, sixteen and thirty-two cells arranged in a solid 

 sphere or morula. As the next step in development a cavity ap- 



