218 



Fig. 53. Diagrammatic representation of a section of the body wall of Spon- 

 gilla (with few alterations after Delagk and Hérottard). cnli. = 

 conulus; p. = ostia; os. = osculum; os. i. ::= oscular tube; ects. 

 = ectosome; cv. hy. = subdermal cavity; en. inh. = incurrent 

 canal; cn.exh. = excurrent canal; c/is. = parenchyma; the arrows 

 indicate the direction of the water current. See p. 119 — 120. 



Fig. 54. Flagellated chambers and surroundings in Spongilla. ft. ch. = 

 flagellated chamber; inc. can. = incurrent canal; exc. can. = 

 excurrent canal. Magnif. ± 130 times. The arrows indicate the 

 direction of the water current. See p. 120. 



Fig. 55. Section of a flagellated chamber of Spongilla (magnif. + 1600 times), 

 after Yosmarr and Pekelharing, ap. = apopyle. See p. 120. 



Fig. 56. Successive stages of the flagellar movement of an isolated choa- 

 nocyte. The cell body is still connected with several other choa- 

 nocytes, the collar is entirely retracted. The arrows indicate the 

 direction of the water current, the dots floating particles; the 

 moment of observation is given in each case; a. immediately 

 after isolation; in e. the flagellum has finally come to rest. Magnif. 

 ± 1770 times. See p. 126—127. 



Fig. 57. As Fig. 56. The collar is partly retracted, a. immedately after 

 isolation; in c. the flagellum has come to rest; in d. — e. a (new) 

 period of weak motion began again, which is finished in f. Magnif. 

 ± 1770 times. See p. 128. 



Fig. 58. Successive stages of the flagellar movement of a number of cho- 

 anocytes still joined within a part of a flagellated chamber, 

 observed in a ravel preparation. The collars are entirely retracted. 

 a. immediately after isolation, in c. the flagella have finally come 

 to rest. Cnf. Figs. 56—57. See p. 128, 132. 



Fig. 59. Intact flagellated chamber of living Spongilla grown on cover- 

 glass; the flagella in the normal spiral- or undulating-motion. 

 The collars are fully expanded, ch.l. = choanocytic layer; odr.= 

 oildrops. Magnif. ± 1430 times. See p. 130—131. 



Figs. 60 — 62. Representation of flagellum and collar seen on top; in Fig. 60 

 the flagellum stops, in Fig. 61 it is in spiral-motion, in Fig. 62 in 

 flat undulating-motion. See p. 131 — 132. 



Fig. 63. Diagrammatic representation of the water current inside a flagel- 

 lated chamber of Spongilla. pr.p. — prosopyle; ap.p. = apopyle; 

 the arrows indicate the direction of the current; -f and — refer 

 to the water pressure. See p. 132—134. 



Fig. 64. Semi-diagrammatic representation of a chamber, the flagella of 

 which are beating with the tops outside the apopyle. ch. I. = 

 choanocytic layer. See p. 135—136. 



Fig. 65. The different ways of capturing (food-)particles within a flagel- 

 lated chamber of Spongilla (diagrammatic). The prosopyles have 

 not been drawn, nor the separate cells of the choanocytic layer 

 {ch.l). The way taken by the particles is indicated by dots. 

 a. and h. show the capturing between the bodies of the choano- 

 cytes; c. the capturing between the collai-s; d. the capturing at 

 the bases of the collars. See p. 143—145, 



