1906] YAMANOUCHI—POLYSIPHONIA VIOLACEA 4II 
The sperm when detached is oval in form (fig. 73), and has a thin 
wall derived from the mother cell, and a large vacuole occupies almost 
all the cell cavity. The cytoplasm is therefore forced to lie in a thin 
layer under the cell wall, and the nucleus occupies the larger end of 
the oval. The chromosomes maintain their individuality and are 
connected with one another by delicate linin threads (jigs. 74, 74a). 
The nucleus remaining in the sperm mother cell after the formation 
of the first sperm divides at once, passing through prophase (jig. 75), 
metaphase (jigs. 76, 78), and anaphase stages (jigs. 79, 80), following 
the same history as in the previous mitoses. Here is apparent also 
the same conspicuous difference in the form of the nucleus between 
prophase and metaphase (figs. 75, 76), 20 chromosomes (fig. 77) 
always appearing in this critical stage. Finally, the telophase of 
Mitosis is followed by cell division through a cleavage furrow, which 
cuts off the second sperm (fig. 8r) in a similar manner to the first. 
The nucleus which remains in the sperm mother cell may repeat the 
Process, forming a third sperm. 
The successive formation of sperms by constriction from the sperm 
mother cell may be compared, in a general way at least, to the pro- 
cess of formation of conidia in certain groups of fungi, where the 
conidia are developed successively by constriction from a conidiophore. 
Of course such a comparison is a superficial one, since conidia are 
Y NO means comparable to sperms in the phylogenetic sense. The 
Spermatia found in the rusts and lichens, and certain antheridia of 
the Laboulbeniaceae present greater resemblances. THAXTER (78) 
describes an exogenous method of sperm formation in Ceratomyces 
and Zodiomyces, in which sperms are developed successively from a 
definite point at the distal end of fertile cells of the antheridial branches, 
agreeing thus with the process in Polysiphonia. 
Wotre (86) considers the sperm of Nemalion to be the homologue 
of an antheridium because the sperm nucleus divides into two. No 
Mitosis was found in the sperm of Polysiphonia, although this 
Matter received careful attention. The sperm of Nemalion also 
“scapes as a naked or thin-walled protoplast from the parent cell- 
‘Membrane, while that of Polysiphonia becomes detached and retains 
the parent cell wall. The differences, however, do not seem to the 
author to affect the relationship of these two sperms as homologous 
Sttuctures. That of Polysiphonia is also the homologue of a uni- 
