226 THE ROTANTCAL MAGAZINE. LVoi. xxxv. no. 4-2o. 



of the new frustule, it breaks up at the side. I could not exactly 

 observe where it breaks up, but as the hypotheca is seen closely 

 adhered with the remained portion of the perizonium, one can imagine 

 that it breaks up thereabout. The cell-division is made in succession 

 and a new chain is tlms completed. 



Th;.^ daughter-chain consists of 8 or 9 cells, seldom of 12, and 

 it still remains attached to the old frustule. When the cells of the 

 newly formed chain multipl}' by repeated cell-division to 12 or more 

 in number, the chain detaches from the remaining portion of the 

 perizonium. It is noteworthy that the primary hypotheca i.e., the 

 valve formed in the auxosporc near the mother cell has a subconical 

 or subcylindrical outline, and has no seta. These are the characters 

 which differing from the cases already studied by me in Ch. dcbile 

 and others. 



Setae on the hypotheca may perhaps be formed after the daughter- 

 chain has detached from the mother frustule. Thus the cells in the 

 daughter-chain recover their own natural sizes and their breadth is 

 If — 2\ broad as that of the old frustule (Fig. 6.). 



In the classifying Chactoceras, shape and size of the cells, 

 characters of setae and number and form of chromoplasts are the 

 most important points, also resting spores. In the present species, 

 we often met with resting spores formed almost at the middle portion 

 of the mother cell. Both valves of the resting spores are vaulted, 

 with the lower valve usually less vaulted than the upper. The upper 

 valve has a short cylindrical girdle band which is closely stuck to 

 the mother cell. The resting spore contains one nucleus and many 

 chromatoi)hores situated along the wall and many oil drops as reserve 

 materials. The upper valve has a crown of puneta on its margin 

 which is well illustrated by Gran.^J Gran states that the spore 

 figured by Cleye belongs without doubt to this species {Ch. teres ), 

 the fine hairs in the lower valve are very difficult to see and their 

 occurrence does not appear to be constant. On the contrary, the 

 spore figured by Mangin' has a wreath of fine hairs (ca. 30 /^ long.), 

 on its lower valve. I have seen both crowns of puneta and hairs 

 formed on one and the same resting spore. The character of the 

 resting spore at the beginning of its development is quite similar to 



1) Gkan: Den Norske Nordhavs Expedition. Bot. Protophyla. p. 36. PI. Ill, 

 Figs. 33 & 36. 



2) Mangin: riivtoplancton de la Croiere dii E6ne dans I'Atlantique. I'.iOS. 

 p. 52, Fig. 40, II. 



