157 



Note on the Method of Feeding of Phyllopods and 



Cladocera. 



By Marcus Hartog, M.A., D.Sc. 



{Communicated June 2l.st, 1901.) 



In the course of some hatching experiments with Ajnts and 

 BrancMpus I incidentally noticed that they fed lying on their 

 backs, the swing of the appendages producing a backward current 

 of the water down either side, while the inmost lobes (" gnatho- 

 basites " of Lankester) sent an upstream along the median line to 

 the mouth. The food consisted of the floating materials in the 

 water, and was swallowed by the combined movements of 

 the mandibles and the peristaltic action of the gullet. The two 

 mandibles work so that the one has greater play than the other, 

 carrying the suspended matters past it right into the gullet. 



It is interesting to compare this with the more complex 

 arrangements of Cladocera. To study these in Daphnia, etc., 

 we require a good magnification by a low-angle lens, such as 

 the B (I in.) and C (5 in.) of Zeiss; and the animal must lie in 

 a cell, preferably uncovered, deep enough to allow it free play. 

 Here the thoracic appendages cause a flow of water into the 

 shell through the angles on either side between the valves and 

 the beaked head, and immediately past the anterior antennae, 

 which are thus in the very best position, as sense organs, for 

 perceiving any change in the properties of the indraught. The 

 stream flows backwards between the valves in the space traversed 

 by the limbs proper and their pectinate plates. Into the gill- 

 cavities, between the valves and the outer side of the limbs, no 

 formed particles can be seen to pass, as the pectinate plates on 

 the limbs, which make them so eflicient in producing the current, 

 are equally efficient as sieves or filters. The solid particles in 



JouRN. Q. M. a, Series II.— No. 49. 11 



