No. 647] PROGRESSION OF LIFE IN THE SEA 493 



ming flagellate, such as we so often find brought about by 

 the deposition of calcareous plates or silicious spicules 

 or the production of ridges or furrows, would tend to 

 slow down its speed of travel, from increased friction 

 with the surrounding water. This would have a similar 

 effect to actual fixation in drawing floating particles by 

 the action of the flagellum, and also lead to animal nutri- 

 tion. Still another development would occur when the 

 fallen flagellate began to creep along the sea-floor by 

 contractile movements of the plasmic surface, losing its 

 flagellum, and adopting the mode of life of an amoeba. 

 That amoeba and its allies, the Ehizopods, are descended 

 from a flagellate ancestor is a view suggested by Lan- 

 kester" in 1909, which was adopted by Doflein," and is 

 now strongly advocated by Pascher as a result of much 

 new research. 



The transformation from the plant to the animal mode 

 of feeding we can see in action by studying actual organ- 

 isms which exist to-day. In the course of my work al- 

 ready referred to on the culture of plankton organisms 

 there has on several occasions flourished in the flasks a 

 small flagellate belonging to the group of Chrysomonads, 

 which was first described by Wysotzky under the name of 

 Pedinella hexacostata, and to which I drew the attention 

 of Section D at the Cardiff Meeting in 1920. The general 

 form of Pedinella resembles that of the common Vorti- 

 cella, but its size is much smaller. The body, which is 

 only about 5 ft in diameter, is shaped like the bowl of a 

 wine glass, and from the base of the bowl, which is the 

 posterior end, a short, stiff stalk extends. From the 

 center of the anterior surface there arises a single long 

 flagellum, surrounded at a little distance by a circle of 

 short, stiff, protoplasmic hairs. Arranged in an equa- 

 torial ring just inside the body are six or eight brownish- 

 green chromatophores or chloroplasts. In a healthy cul- 



isLankester, "Treatise on Zoology," Part T, London, 1909, p. xxii. 

 "Doflein, "Protozoenkuiide," 1916. 



"Paseher, Archiv f. Frotistenkunde, Bd. 36, 1916, p. 81, and Bd. 38, 

 1917, p. 1. 



