,22 



DEPTHS OF THE OCEAN 



Bergon. 

 Karsten. 



Peridineae. 



which, according to Bergon's investigations^ would seem to be 

 zoospores, and which Karsten assumes to be sexual cells. 

 Karsten has observed the formation of microspores in an 

 antarctic diatom, Corethroii valdivicE (see Fig. 225), and in the 

 same microscopic preparations found amalgamations of small 

 cells resembling microspores. We cannot yet, however, consider 

 this conclusively settled. We do not know the life-history of 

 the numerous small spores after they have emerged from the 

 mother-cell. We can only hope that the centrifuge will enable 

 us to study the 

 most diminutive 

 andsensitivecells 

 immediately after 



capture, and that ^ ^ ¥ } II ^ 



we shall thus suc- 

 ceed in solving 

 this problem in 

 the biology of 

 diatoms. 



H 





Fig. 225.— Microspore-formatio.\ 01 Cokethron valdivi.e 

 in different development stages (="-1"). 



Ripe microspores in the cell to the right. (Karsten.) 



Peridinese are 

 mobile algae fur- 

 nished with two 

 cilia. Several 

 species can pro- 

 duce brilliant 

 phosphorescence. 

 Their cells are 

 highly organised, 

 with adistinctdif- 

 ference between 

 the anterior and 

 posterior ends, and between the dorsal and ventral faces. 

 The cell-wall is built up entirely of organised matter, which 

 dissolves soon after the death of the cell. Peridinese are 

 therefore not noticeable in the deposits of the ocean -bottom, 

 which is one of the reasons why, until quite recently, they were 

 but slightly and imperfectly known. A number of laminae, 

 characteristic in shape and position, compose the cell-wall. On 

 the posterior side there is a characteristic furrow, with a pore 

 for one of the cilia, which can be withdrawn spirally into a 

 sheath (see Fig. 226). The ventral furrow is often protected 

 by curtain-membranes. Another furrow encircles the cell, and 



