T907] AFOGAAIV IN NEPHRODIUM 145 



in size and assumes gradually a coiled band shape, while the nucleus, 

 after an interesting modification of chromatin material, becomes 

 also a coiled structure. The cilia appear only on the outer surface 

 of the blepharoplast. The Nebenkern remains attached at the 

 posterior end of the mature sperm, with the remnant of cytoplasmic 

 material. 



Oogenesis and jertilization. — In the formation of an archegonial 

 initial from a vegetaltive cell of the prothallium, 64 or 66 chromosomes 

 are present. The mitoses which occur in the formation of the cen- 

 tral cell; neck and ventral cells, and neck canal, ventral canal, and 

 egg cells, have very interesting peculiarities which will be described in 

 a later paper. The noteworthy thing is that the number of chromo- 

 somes is 64 or 66. 



Sperms pass through the archegonial neck and reach the egg cell. 

 Normally a single sperm succeeds in entering, through the cytoplasm, 

 into the egg nucleus which is in the resting condition. Within the 

 egg the sperm finally loses its individual outline. 



The fertilized egg nucleus in the resting state passes into the pro- 

 phase of the first segmentation division. The spirem is a homogeneous 

 thread structure, uniform in thickness, and seems to be continuous. 

 It segments into a number of chromosomes that become arranged in 

 an equatorial plate. The chromosomes in the equatorial plate split 

 longitudinally and two sets of daughter chromosomes separate and 

 pass toward the poles of the spindle. The polar view of this set shows 

 that the number of chromosomes is 128 or 132. 



The further processes of segmentation divisions during the develop- 

 ment of an embryo were traced out in order to make certain the number 

 of chrosomomes, and 128 or 132 are always present. 



Apogamy, — The prothallia which produce ajx^gamous sporophytes 

 do not seem to be different from those which form normal embryos, 

 so long as they remain a single cell layer in thickness throughout. The 

 morphological structure does not seem to show any peculiarity. Num- 

 erous antheridia are produced. Although the mitoses which give rise 

 to sperm mother cells from a primary spermatogenous cell are different 

 from those of a normal case, yet the motile sperms are developed. 



The most important and peculiar feature of the prothallia m 

 connection with apogamous growth is as follows: The successive 



