430 SELIG HECHT 



a row of cilia on each side of these shts, there are in all about 

 384,000 short rows (ca. 0.2 mm. long) of cilia lashing water 

 through the pharynx of the animal. 



Such water currents are not uncommon among marine animals. 

 They have been studied elaborately in Lamellibranchs by Wal- 

 lengren ('05); and the work of Orton and of Andrews ('93) has 

 shown how similar the mechanism of their production is in 

 Lamellibranchs, Ascidians, and Amphioxus. The details of 

 the maintenance of such currents in the gastrovascular system of 

 Aurelia (Widmark '13) have brought to light the long suspected 

 fact that, unlike Amphioxus, Tunicates, and Sponges (Parker 

 '10 and '14), muscular movements are an important factor in 

 reinforcing the ciliary current produced by medusae. 



2. Respiration (cf. however, Dakin, '09, p. 52; Putter '07, 

 Tab. V) and the gathering of plankton organisms (Orton, p. 20) 

 are the two functions commonly ascribed to the incoming cur- 

 rent. To these. Putter ('07) has proposed the addition of a third. 

 On the basis of metabolism studies, he believes that plankton 

 food is insufficient for the carbon requirement of a variet}^ of 

 marine animals, "and that sea- water constitutes a very dilute 

 nutrient solution, from which they resorb their food entirely 

 or in part" (Putter, '14, p. 98). To the water current, then, 

 falls the task of bringing this 'nutrient solution' to the place 

 where it may be resorbed.'^ 



I mention Putter's conclusions because he, and others who 

 have criticised him (Lipschiitz, Moore et al.) make frequent 

 assumptions as to the volume of the current produced by various 

 animals, having, however, almost no accurate quantitative 

 data on which to base their statements (Putter '07, p. 293). 



The velocity measurements made by Wallengren (p. 23) 

 on the anal current in mussels, and the roughly accurate estima- 

 tion of the volume of water passing through the Gehause of an 

 appendicularian, made by Lohmann ('09, p. 220), show that the 

 quantities are rather large. The only values actually determined 

 are those found by Parker ('14) for a Bermuda sponge. A finger 



3 An actual case of such a resorption (really a synthesis, too) has just been 

 demonstrated for fats by Churchill ('15) with the fresh water mussel. 



