Dec, im.i ON THE FORMATION OF AUXOSPOBES 225 



only 011C pore.^^ As to the significance of the formation of two 

 pores, I can not explain, but it may be supposed that the liberation 

 of cell-contents may then more easily be performed. 



In the early stage of liberation of cell-contents the nucleus glides 

 out into the portion bulged out and takes its position at the distal 

 end from the mother cell. (Fig. 2.). The chromoplasts now remove 

 outwards and occupy their xmrietal position. The whole i)lasma 

 thus liberated takes an almost spherical shape of about 40 /i in 

 diameter and attaches itself at the pore of exit. The cell content 

 thus liberated transforms to the auxosporc and the mother cell now 

 becomes empited. (Figs. 3-4.). 



But, a few fine protoplasmic threads are often seen connecting 

 the libei-ated plasma which soon swells up to a certain bulk and 

 gradually assumes a short subcylindrical shape, whose major axis is 

 usually perpendicular to the axis of the n\other-chain, though it 

 yield to the movement of the medium. 



The auxospore is covered with the distinct membianes; the 

 outer, so called " Perizonium " and the inner membrane. At the 

 beginning, the inner membrane is very difficult to detect as it is very 

 thin and closely lines the perizonium, while the outer one or perizo- 

 nium is thick and well defined. The distal side of the inner membrane 

 covering the liberated plasma, takes a definite shape so as to make 

 the upper valve (epitheca), and from the two corners of the epitheca, 

 setae soon begin to make their appearance and as they elongate they 

 stretch out through the thick perizonium. In the next place, the 

 mantle part or girdle becomes well defined and finally the lower valve 

 (hypotheca) is formed (Fig. 4 & 5.). In this stage the inner mem- 

 brane may easily be demonstrated and auxospore is now fully formed 

 being coated with the silicified cell-well (the inner membrane). 



As soon as an auxospore fully grows to a newly enlarged cell 

 with an elongated frustule, it is ready for the cell-division. Nucleus 

 and cytoplasma are divided into two and chromoplasts are carried 

 to each of them in equal numbers ; the height of frustule is increased 

 and setae make their appearance (Fig. 4 & 5 ). 



As the perizonium can not extend itself to follow the size-increase 



1) These species have one pore, tiowever, tlie jierforalion in Ch. dehile is a; 

 the middle of the broader girdle and in others,— C%. scoloj.endra, CJi. eonslridum, Ch. 

 didymum, and Ch. compressum, is found in the narrower girdle. Auxospore-i'ormation 

 of Cli. .scolopc'idra has not been reported. It takts place in it in tlie same manner as 

 in Ch. debile see Test-figures)- 



