Marine Plankton from the East-Greenland Sea. 



273 



coastal water and present also both in Danmarks Havn and in the 

 inner border of the pack-ice. hi August 1906 it was not uncommon 

 at ca. 13° W. Long., and dominant in the samples taken along the 

 coast from Koldewey Island to Cape Amélie; in October 1906 some 

 specimens were found in Danmarks Havn, but mostly empty fru- 

 stules. In August — September 1907 sjngle specimens occurred in the 

 samples from Danmarks Havn. In July 1908 it was dominant in 

 Danmarks Havn and from that place northwards along the coast 

 until ca. 78° N. Lat., and it was further found in some samples a 

 little more eastwards, until ca. 11° W. Lat. 



In some of the samples from August 1906 

 and July 1908 taken in the coastal water (the 

 temperature of the water being between -f- 0,5 

 and 4,2°) I often found chains in which the 

 awns of many of the cell-walls had aborted. 

 As the fig. 8 shows, such a chain gets a rather 

 curious aspect : The two latest divisions of the 

 chain figured have produced new cells which bear 

 no awns from the valves while the oldest divi- 

 sion has given normally developed awns of which 

 only the bases have been drawn. At the places ..I^^^^^^$5< 

 of the awns we find only small protuberances 

 on the valves, and the protuberances of two 

 cohering valves correspond to each other. It 

 looks as if the cell-division has stopped too 

 early, when only the division of the contents 

 has been fulfilled and the development of the 

 foramen has begun. In some cells I found very 

 short and curved awns in stead of the protu- 

 berances, thus showing the reduction in a some- 



what less degree. 



Fig. 8. Chaetoceras 



boréale Bail, with 



ahorted awns. 



500 t. m. 



I have no real explanation of the pheno- 

 menon. Perhaps it shows that the cell-division 

 takes place very rapidly, or perhaps it designates 



a state of hunger, or perhaps it has something to do with micro- 

 spore formation, as it occurred in the some samples in which mi- 

 crospore formation in Ch. decipiens was observed (but no microspores 

 were found in Ch. boréale!). К. Okamura (Bot. Magaz., Tokyo, XXI, 

 1907, pi. Ill, fig. 36) has figured the same phenomenon in a chain of 

 Ch. criophihim, but has no remarks on it in the text, while in the 

 explanation of the figures the says (p. 105): "One of the cells of 

 another chain many times divided". 



Also G. Karsten (Valdivia-Exp., Phytoplankton des antarkt. Mee- 

 XLIII 21 



