384 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY. 



Biddulphia sinensis, as in figs. 6, 7 and 9. The other 

 daughter cell in figs. 6 and 8 will apparently give rise 

 to a cell very like the parent, and the ends will again be 

 unlike. On the other hand, figs. 8, 10, 14 and 15 show 

 that while one of the daughter cells may give rise to a 

 sinensis-mobiliensis form, the other will produce a form 

 closely approaching that of a true mobiliensis . Fig. 4 

 shows very distinctly two daughter cells of which the 

 external ends are clearly of the sinensis type, but the 

 internal ends where division is taking place are assuming 

 a characteristic mobiliensis appearance. When division 

 is completed we would arrive at the first stage 

 of the transition of Biddulphia sinensis into sinensis- 

 mobiliensis, then later at the next division probably we 

 should have two apparently distinct Diatoms, Biddulphia 

 sinensis and B. mobiliensis. We have noticed that when 

 Biddulphia made its appearance in the autumn collections 

 from Port Erin Bay during the last two years B. sinensis 

 was at first the prevailing form. B. m,obiliensis then 

 becomes more plentiful • later in the winter and in 

 the following spring, when B. sinensis diminishes in 

 numbers. 



Gran, who reports on the pelagic plant life in 

 " Depths of the Ocean," by Sir John Murray and 

 Dr. Johan Hjort, refers to the known case of the Diatom 

 Rhizosolenia hebetata occurring in two perfectly distinct 

 forms. On p. 320 he describes the differences in the 

 cell-walls and setae of Chaetoceras decipiens in spring 

 and summer, and the variation in size and shape between 

 specimens of Biddulphia aurita from along the Arctic 

 coasts and off the south of Norway. He says : " We find 

 " a variation of a different nature in the case of Rhizoso- 

 ": lenia hebetata. It occurs in two perfectly distinct 

 " forms, that were formerly regarded as good species. 



